SecProbe.io

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   WHITE                               Attorneys and Counselors at Law
KOCH, KELLY                            John F. McCarthy, Jr.
     &                                 Benjamin Phillips
   McCARTHY                            Albert V. Gonzales
A Professional Association             C.W.N. Thompson, Jr.
                                       M. Karen Kilgore
                                                             Suzanne Odom
                                       Sandra J. Brinck
                                       Aaron J. Wolf
                                       Mary E. Walta
                                       Rebecca Dempsey    Special Counsel
                                       John M. Hickey     Paul L. Bloom
                                       Julia Wittenberger-Wagner
                                       Julia B. Rose

                                 February 17, 2005

Patricia A. Williams
Division of Investment Management
Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C.  20549                         Via EDGAR Correspondence

Re:  Thornburg Investment Trust
     Registration Number Under the Securities Act of 1933:  33-14905
     Registration Number Under the Investment Company Act of
     1940:  811-05201

Dear Ms. Williams:

     We filed on December 1, 2004 post effective amendment number 62 to
the Registration Statement on form N-1A of Thornburg Investment Trust.
The amendment became effective on February 1, 2005, in accordance with
Rule 485 (a)(1) under the Securities Act of 1933.  We subsequently filed
on February 7, 2005, in accordance with Rule 497, definitive versions of
the three prospectuses and three statements of additional information
which were components of the December 1, 2004 amendment.

     I outline below revisions made to the amendment and reflected
in the documents filed on February 7, 2005.  I do not comment on minor
corrections, conforming changes, grammatical corrections and similar
revisions.

433 Paseo de Peralta    Post Office Box 787    Telephone (505) 982-4374
Santa Fe, NM  87501    Santa Fe, NM 87504-0787       Fax (505) 984-8631
                        e-mail cwnt@wkkm.com

                                                   Patricia A. Williams
                                                      February 17, 2005
                                                                 Page 2

Thornburg Funds Prospectus (Classes A, B, C and D Shares), February 1,
2005
__________________________

     1.  We have inserted under the caption "Past Performance of the
         Fund"for each Fund the total return information as of December
         31, 2004, together with the corresponding returns for the
         index against which each Fund's returns are compared.  In a
         few cases we also updated the highest or lowest quarterly
         results, where required.

     2.  We conformed bar chart scales for the Funds, so that fixed
         income Funds conformed to one scale, and equity Funds
         conformed to another scale.

     3.  We changed the index used to compare performance for Limited
         Term National Fund from the Lehman Five Year General Obligation
         Bond Index to the Lehman Five Year Municipal Bond Index.

     4.  We changed the index used to compare performance for Limited
         Term California Fund from the Lehman Five Year General
         Obligation Bond Index to the Lehman Five Year Municipal Bond
         Index.

     5.  Footnote (4) to the Annual Fund Operating Expenses table for
         Government Fund was revised to add a statement that the
         investment adviser and principal underwriter intend to waive
         fees and reimburse expenses so that actual Class B expenses
         do not exceed 2.50%.

     6.  We changed the index used to compare performance for Income
         Builder Fund.  Previously, total returns were compared to the
         Standard & Poor's Composite Index of 500 Stocks.  Currently,
         returns are compared to a "blended benchmark" comprised of 25%
         Lehman Brothers Aggregate Bond Index, and 75% MSCI World
         Equity Index.  Both indices are broad measures of market
         performance, but the first measures the bond market and the
         second measures domestic and foreign equity markets.  In
         addition, we added a footnote to the tables which describes
         the basic components of each of these indices.

                                                   Patricia A. Williams
                                                      February 15, 2005
                                                                 Page 3

     7.  We deleted from footnote (4) to the Income Builder Fund Annual
         Operating Expenses table a statement that the investment
         adviser will reimburse expenses so that actual Class A expenses
         will not exceed 1.60%, because that class is currently accruing
         expenses at a lower rate.

     8.  We deleted from the fourth paragraph appearing under the caption
         "Buying Class A Shares" a sentence stating that investors should
         retain their account information because it appeared redundant
         with the balance of the paragraph.

     9.  We revised and simplified the description of accounts which can
         be combined by investors to obtain the "rights of accumulation"
         discount.  This language appears under the caption "Rights of
         Accumulation."

    10.  We deleted one of the variations from the public scale of sales
         charges for Class A shares, which appeared under the caption
         "Proceeds From a Load Fund Redemption."

    11.  In response to a staff comment, we deleted from the second
         paragraph appearing under the caption "Excessive Trading" a
         statement that the Funds could, in the circumstances described,
         "cancel any purchase or exchange order" and also deleted the
         sentence "The Funds further reserve the right to delay for up to
         one business day the processing of any exchange requests."

    12.  We deleted from under the caption "Federal Tax Treatment of
         Sales or Redemptions of Shares" a statement that gains on
         certain redemption would be capital gains for federal income tax
         purposes.  We also deleted a statement from the second paragraph
         following stating that two of the Funds, would provide
         information as to the percentage of income derived from Treasury
         securities.

                                                   Patricia A. Williams
                                                      February 15, 2005
                                                                 Page 4

Institutional Class Shares Prospectus (Class I), February 1, 2005
__________________________

    13.  We have inserted under the caption "Past Performance of the
         Fund" for each Fund the total return information as of December
         31, 2004, together with the corresponding returns for the index
         against which each Fund's returns are compared.  In a few cases,
         we also have updated the highest or lowest quarterly results,
         where required.

    14.  We conformed the bar chart scales for the Funds, under the
         caption "Past Performance of the Fund," so that fixed income
         Funds conform to one scale, and equity Funds conform to another
         scale.

    15.  We changed the index used to compare performance for Limited
         Term National Fund from the Lehman Five Year General Obligation
         Bond Index to the Lehman Five Year Municipal Bond Index.

    16.  We changed the index used to compare performance for Limited
         Term California Fund from the Lehman Five Year General
         Obligation Bond Index to the Lehman Five Year Municipal Bond
         Index.

    17.  We added to the last paragraph under the caption "Principal
         Investment Strategies" for Growth Fund a statement that
         portfolio turnover may exceed 100% per year.

    18.  We changed the index used to compare performance for Income
         Builder Fund.  Previously, total returns were compared to the
         Standard & Poor's Composite Index of 500 Stocks.  Currently,
         returns are compared to a "blended benchmark" compromised of 25%
         Lehman Brothers Aggregate Bond Index, and 75% MSCI World Equity
         Index.  Both indices are broad measures of market performance,
         but the first measures the bond market and the second measures
         domestic and foreign equity markets.  In addition, we added a
         footnote to the table which described the basic components of
         each of these indices.

                                                   Patricia A. Williams
                                                      February 15, 2005
                                                                 Page 5

    19.  In response to a staff comment, we deleted from the second
         paragraph appearing under the caption "Excessive Trading" a
         statement that the Funds could, in the circumstances described,
         "cancel any purchase or exchange order" and also deleted the
         sentence "The Funds further reserve the right to delay for up
         to one business day the processing of any exchange requests."

    20.  We deleted from the first paragraph under the caption "Dividends
         and Distributions" a statement respecting notifications
         respecting characterization of distributions.

Thornburg Retirement Plan Shares Prospectus(Classes R-1 and R-5),
February 1, 2005
__________________________

    21.  We have inserted under the caption "Past Performance of the
         Fund" for each Fund the total return information as of
         December 31, 2004, together with the corresponding returns for
         the index against which each Fund's returns are compared.
         In a few cases we also updated the highest or lowest quarterly
         results, where required.

    22.  We conformed bar chart scales for the Funds, so that fixed
         income Funds conform to one scale, and equity Funds conform to
         another scale.

    23.  We have increased the estimate for "other expenses" for the new
         class of shares of each of the Funds to 1.20% for the first
         fiscal year this class of shares is available.  The designation
         of this class also has been changed from "R-3" to "R-5" for each
         Fund.

    24.  We have revised footnote (3) to the Annual Fund Operating
         Expenses Table for Government Fund, Income Fund, Value Fund
         and International Fund to delete the words "current actual" in
         stating that the displayed expense ratio is not representative,
         and replacing the deleted words with the word "expected."  The
         sentence now reads "Other expenses for Class R-1 shares are
         based on expenses for the fiscal year ended September 30, 2004,
         which appear disproportionately high because the class assets
         were relatively small for much of the year, and are not
         representative of expected expenses."

                                                   Patricia A. Williams
                                                      February 15, 2005
                                                                 Page 6

    25.  We added a statement to footnote (5) under Government Fund's
         Annual Fund Operating Expenses table that the investment adviser
         and the principal underwriter intend to reimburse expenses and
         waive fees so that actual Class R-5 expenses do not exceed .99%.
         We also added another footnote stating that Class R-5 shares are
         not available for this Fund as of the date of the Prospectus.

    26.  We added to the explanation of the expense example table for
         Government Fund, Income Fund, Value Fund and International
         Fund a further explanatory note which reads: "In accordance
         with regulatory requirements, no five or ten year figures are
         provided for Class R-5 shares, because this is a new class of
         shares."

    27.  We added a statement to footnote (5) under Income Fund's
         Annual Fund Operating Expenses table that the investment
         adviser and the principal underwriter intend to waive fees and
         reimburse expenses so that actual Class R-5 expenses do not
         exceed .99%.  We also added another footnote stating that Class
         R-5 shares are not available for this Fund as of the date of the
         Prospectus.

    28.  We added a statement to footnote (5) under Value Fund's Annual
         Fund Operating Expenses table that the investment adviser and
         the principal underwriter intend to waive fees and reimburse
         expenses so that actual Class R-5 expenses do not exceed .99%.

    29.  We added a statement to footnote (5) under International Value
         Fund's Annual Fund Operating Expenses table that the investment
         adviser and the principal underwriter intend to waive fees and
         reimburse expenses so that actual Class R-5 expenses do not
         exceed .99%.

    30.  We added statement to footnote (5) under Growth Fund's Annual
         Fund Operating Expense table that the investment adviser and the
         principal underwriter intend to waive fees and reimburse
         expenses so that actual Class R-5 expenses do not exceed .99%.
         We also added another footnote stating that Class R-5 shares are
         not available for this Fund as of the date of the Prospectus.

                                                   Patricia A. Williams
                                                      February 15, 2005
                                                                 Page 7

    31.  We changed the index used to compare performance for Income
         Builder Fund.  Previously, total returns were compared to the
         Standard & Poor's Composite Index of 500 Stocks.  Currently,
         returns are compared to a "blended benchmark" comprised of 25%
         Lehman Brothers Aggregate Bond Index, and 75% MSCI World Equity
         Index.  Both indices are broad measures of market performance,
         but the first measures the bond market and the second measures
         domestic and foreign equity markets.  In addition, we added a
         footnote to the table which describes the basic components of
         each of these indices.

    32.  We added a statement to footnote (5) under Income Builder
         Fund's Annual Fund Operating Expenses table that the investment
         adviser and the principal underwriter intend to waive fees and
         reimburse expenses so that actual Class R-5 expenses do not
         exceed .99%.  We also added another footnote stating that Class
         R-5 shares are not available for this Fund as of the date of the
         Prospectus.

    33.  In response to a staff comment, we deleted from the second
         paragraph appearing under the caption "Excessive Trading" a
         statement that the Funds could, in the circumstances described,
         "cancel any purchase or exchange order" and also deleted the
         sentence "The Funds further reserve the right to delay for up to
         one business day the processing of any exchange requests."

    34.  The first paragraph under the caption "Dividends and
         Distributions" was revised to state that Growth Fund is expected
         to follow the practice of Value Fund and International Value
         Fund in declaring and paying any not investment income
         quarterly.

    35.  The advisory fee table under the caption "Investment Adviser"
         was revised to include inf