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April 20, 2006

Mr. James Allegretto
Senior Assistant Chief Accountant
United States Securities and Exchange Commission
Division of Corporate Finance
Washington, D.C.  20549-0404

Re:  Unitil Corporation
     Form 10-K for the calendar year ended December 31, 2005
     Filed February 22, 2006
     File No. 001-08858

Dear Mr. Allegretto:

          Set forth below are the responses of Unitil Corporation (the
"Registrant", "Unitil" or the "Company") to the letter dated March 31, 2006 (the
"Comment Letter") from the Staff (the "Staff") of the Division of Corporation
Finance of the Securities and Exchange Commission (the "Commission") concerning
the Registrant's Annual Report on Form 10-K (the "Form 10-K"), which was filed
with the Commission on February 22, 2006.

          For your convenience, the Staff's comments have been set forth in bold
and the numbered paragraphs contained herein correspond to the numbered
paragraphs in the Comment Letter.

Corporate Office
----------------

6 Liberty Lane West
Hampton, NH  03842-1720

Phone:  603-722-0775

<PAGE>

Mr. James Allegretto
U.S. Securities and Exchange Commission
April 20, 2006
Page 2

Item 7 Management's Discussion and Analysis
--------------------------------------------

     1.  Therm Sales, page 23
     ------------------------

     We note from the table provided on page 23 that firm therm sales decreased
     in 2004 compared to 2003. We also note that in 2004 and 2003 revenue per
     firm therm was $1.24 and $1.15, an increase of 7.8% when comparing 2004 to
     2003. Please explain to us how therm sales decreased and revenue per therm
     increased.

     Response #1:
     -----------
     On a revenue per firm therm basis, the increase of 7.8% in 2004 from 2003
     is attributable to increases in the following components of Total Firm Gas
     Revenue: a) Purchased Gas Revenue, b) Gross Gas Sales Margin, also commonly
     referred to as Base Revenue and c) Conservation and Load Management
     Revenue. Total Firm Gas Revenue per therm increased in 2004 compared to
     2003 due to higher rates billed to customers under each of these revenue
     components. These increases in rates more than offset the impact of a
     decrease in therm sales volumes in the period as discussed below:

     a)   Higher Purchased Gas revenue represents 4.9% of the increase in
          revenue per therm and is due to an increase in the Cost of Gas
          Adjustment Charge rate to recover increased gas commodity prices in
          2004 compared to 2003. Gas commodity prices increased 17.9% in 2004
          compared to 2003.

     b)   Higher Gross Gas Sales Margin represents 2.1% of the increase in
          revenue per therm and is due to higher average gas Base Rates in 2004
          compared to 2003 resulting from an increase in rates authorized by
          regulators to recover pension costs and postretirement benefits other
          than pension costs, as well as differences in the mix of customer
          classes (e.g., residential, commercial, industrial) charged for firm
          therm consumption.

     c)   Higher Conservation and Load Management ("C&LM") revenue represents
          0.8% of the increase in revenue per therm and is due to an increase in
          the C&LM Adjustment Charge rate to recover higher cost associated with
          the development, management and delivery of the Company's energy
          efficiency programs in 2004 compared to 2003.

     In future Management's Discussion and Analysis disclosures, and with due
     attention to critical supporting analyses, Registrant will include
     additional disclosure about the components contributing to changes in
     revenues in the period.

     2.  Operating Expense, page 24
     ------------------------------

     We note from your previous and current Form 10-K that Unitil currently has
     approximately 310 employees compared to 317 in 2004. Please explain the
     reasons for the $0.6 million increase salaries and the $0.5 million
     increase in employee benefit costs in 2004.

<PAGE>

Mr. James Allegretto
U.S. Securities and Exchange Commission
April 20, 2006
Page 3

     Response #2:
     -----------
     Management assumes that this question should have read "...employee benefit
     costs in 2005," based on the amount of cost increases referenced in the
     question.

     The number of employees disclosed in the Company's Form 10-K represents the
     number of employees at December 31 of each year. During the course of each
     year, the number of employees can be higher or lower than the year-end
     figures. During 2004, the number of employees, as of each month end, ranged
     from 310 to 321. During 2005, the number of employees, as of each month
     end, ranged from 308 to 318.

     The $0.6 million increase in salaries and compensation expenses in 2005
     compared to 2004 is due to normal annual increases in salaries for the
     approximately 310-317 employees in 2005 of $0.2 million, which is net of
     the expense savings from the lower number of employees on average. Other
     increases in compensation in 2005 that do not move in a linear relationship
     with number of employees were increased expenses associated with the
     Company's Management and Employee Incentive Plans of $0.3 million and an
     increase associated with the Company's Restricted Stock Plan of $0.1
     million.

     The $0.5 million increase in employee benefit costs in 2005 compared to
     2004 is due to increases in pension and other post retirement benefit costs
     of $0.8 million partially offset by decreases in the costs of health
     insurance and other benefits of $0.3 million. These costs are also not
     directly correlated to the number of active employees.

     In future Management's Discussion and Analysis disclosures, and with due
     attention to critical supporting analyses, Registrant will include
     additional disclosure about the components contributing to changes in costs
     in the period.

     3.  Interest Expense, net, page 26
     ----------------------------------

     Please explain to us the nature of interest on regulatory liabilities.
     Please specifically tell us the regulatory liabilities to which it relates
     and the amount. We may have further comment.

     Response #3:
     -----------
     Certain reconciling rate mechanisms used by the Company's distribution
     operating utilities give rise to regulatory liabilities (and regulatory
     assets) on which interest is calculated. The Company operates a number of
     reconciling rate mechanisms to recover specifically identified costs on a
     pass through basis. These reconciling rate mechanisms track costs and
     revenue on a monthly basis. In any given month, this monthly tracking and
     reconciling process will produce either an under-collected or an
     over-collected balance of costs. In accordance with the Company's tariff,
     interest is accrued on these balances and will produce either interest
     income or interest expense. Interest income is recorded on an
     under-collection of costs, which creates a regulatory asset to be recovered
     in future periods when rates are reset. Interest expense is recorded on an
     over-collection of costs, which creates a regulatory liability to be
     refunded in future periods when rates are reset.

<PAGE>

Mr. James Allegretto
U.S. Securities and Exchange Commission
April 20, 2006
Page 4

     These regulatory interest amounts are combined on the Consolidated
     Statements of Earnings and also combined within the Interest Expense table
     on page 26 of Unitil's Form 10-K for the year-ended December 31, 2005.
     Currently, regulatory assets exceed regulatory liabilities so the net
     effect is interest income in the table. The total interest expense on
     regulatory liabilities for 2005 was $152K and this amount was combined with
     interest income on regulatory assets of $2,677K and disclosed as a net
     amount of interest income on regulatory assets of $2,525K in the table on
     page 26. The primary regulatory liabilities comprising the $152K of
     interest expense in 2005 include: Unitil Energy Systems, Inc. ("UES")
     Transition Service - $66K, Fitchburg Gas and Electric Light Company
     ("FG&E") Energy Efficiency - $42K and FG&E Default Service - $12K and other
     of $32K.

     In the future, the Company will include a separate disclosure of amounts
     and an explanation of interest expense on reconciling rate mechanisms.

Note 2 Equity
-------------

     4.  Restrictions on Retained Earnings, page 58
     ----------------------------------------------

     We note your disclosure regarding the restrictions on retained earnings for
     subsidiaries UES and FG&E. It appears the restrictions wouId require Unitil
     to provide condensed financial information. See Regulation S-X Rule
     5-04(c), Schedule 1. If our understanding is incorrect, please explain why
     you are not required to provide such information.

     Response #4:
     -----------
     Regulation S-X Rule 5-04(c) requires that, when the restricted net assets
     of consolidated subsidiaries exceed 25% of consolidated net assets as of
     the end of the most recently completed fiscal year, condensed financial
     information of the Registrant be included in the filing.

     Management's calculations show that the combined restrictions on the net
     assets for Unitil's wholly-owned subsidiaries UES and FG&E represent 24.2%
     and 24.7% of Unitil's net assets as of December 31, 2005 and December 31,
     2004, respectively. Therefore, in accordance with Regulation S-X Rule
     504(c), management believes that Unitil is not required to provide
     information regarding restrictions on retained earnings and the related
     condensed financial information for these periods because the restricted
     amounts do not exceed 25% of the Registrant's net assets. In Note 2 to the
     Consolidated Financial Statements of the Company in its Form 10-K for the
     year ended December 31, 2005, the Company has elected to disclose the
     restrictions on retained earnings for UES and FG&E because management
     believes that this information would be useful to the reader of the
     financial statements and Notes.

     Management agrees that, if in future periods these calculations result in
     combined restrictions on retained earnings for UES and FG&E that exceed 25%
     of the Registrant's net assets, the Company will provide condensed
     financial information for the Registrant for the corresponding period(s).

<PAGE>

Mr. James Allegretto
U.S. Securities and Exchange Commission
April 20, 2006
Page 5

Note 3 Long-Term Debt. Credit Arrangements. Leases
--------------------------------------------------

     5.  Leases, page 60
     -------------------

     We are unclear on how the renegotiated lease terms resulted in a change of
     classification from a capital lease to an operating lease. In this regard,
     please tell us why such lease originally met the criteria for capital lease
     classification. If due to the lease terms exceeding 75% of the economic
     life, advise us how your original estimated economic life compares with the
     initial 22 year plus anticipated renews ranging from 10-25 years. If due to
     the 90% test, show us the calculation of fair value at inception and
     whether it factored into the useful life of the asset. If so, tell us the
     useful life that was assumed at inception.

     Response #5:
     -----------
     The Company's original lease on its service center used by its
     Massachusetts distribution operating utility, FG&E, was accounted for under
     Statement of Financial Accounting Standards No. 13, ("FAS 13"), Accounting
     for Leases as a capital lease. The original lease met the criteria for a
     capital lease under paragraph 7.d. of FAS 13; the 90% test. Under paragraph
     7.d., when the present value of the lease payments exceeds 90% of the fair
     value of the property at lease inception, the lease is classified as a
     capital lease. This was the case when the original lease, 22 years at
     annual rents ranging from $184,000 to $537,000, began on February 10, 1981.
     The project cost of the building in the original lease was $2,700,000. The
     useful life of the building without regard to the lease arrangement would
     have been 50 years for book accounting purposes.

     When the original lease ended on January 31, 2003; the lessor and lessee
     renegotiated and entered into a new lease for 10 years at level monthly
     payments of approximately $270,000 annually. In the new lease agreement,
     the estimated fair value of the property is $2,640,600. The terms of the
     new lease agreement do not meet the criteria for classification as a
     capital lease under paragraph 7 of FAS 13. As disclosed, the Registrant
     accounts for the new lease as an operating lease.

     6.  FG&E -Electric Division, page 66
     ------------------------------------

     In regards to the investigation by the Massachusetts Department of
     Telecommunications and Energy (MDTE) please provide us with more details as
     to the nature of the investigation. Please provide the most recent status
     of the case along with a detailed analysis of why you believe the outcome
     will not have a material effect on the financial statements.

     Response #6:
     -----------
     The nature of this investigation was originally included in Note #6 -
     Commitments and Contingencies of the Registrant's Form 10-K filed with the
     Commission for the fiscal year ended December 31, 2003 as follows:

     In March 2003, the MDTE opened an investigation into FG&E's dealings with
     Enermetrix, Inc. (Enermetrix). Enermetrix provides an internet-based energy
     auction service that is used by utilities to post their natural gas and
     electric power needs for bids. FG&E used the

<PAGE>

Mr. James Allegretto
U.S. Securities and Exchange Commission
April 20, 2006
Page 6

     Enermetrix Exchange to post its electric default service solicitations in
     September 2001 and March 2002, and Enermetrix earned approximately $19,000
     in fees from these transactions. In Management's view, these successful
     solicitations ultimately resulted in significant lower default service
     costs to FG&E's customers. At the time of these solicitations, FG&E's
     parent, Unitil Corporation, had an approximately 9% ownership interest in
     Enermetrix. The MDTE is investigating whether FG&E is in compliance with
     relevant statutes and regulations pertaining to transactions with
     affiliated companies and the MDTE's Order setting forth the requirements
     for the pricing and procurement of default service. FG&E and the Attorney
     General have completed briefing of the case and an MDTE decision is
     pending. Management believes the outcome of this matter will not have a
     material adverse effect on the financial position of the Company.

     As noted in the more current disclosures (Note #6 - Commitments and
     Contingencies) in the Registrant's Form 10-K for the fiscal years ended
     December 31, 2004 and 2005, the hearing and briefing of the case were
     completed in 2003 and a decision is pending from the Massachusetts
     Department of Telecommunications and Energy ("MDTE"). As of the date of
     this letter, the MDTE has not issued an Order and there has not been any
     active dialogue or correspondence between FG&E, the Attorney General or the
     MDTE regarding this matter since 2003.

     Management believes the outcome of this matter will not have a material
     adverse effect on t