SecProbe.io

February 15, 2013

Via E -mail
Eduardo E. Cordeiro
Executive Vice President and Chief Financial Officer
Cabot Corporation
Two Seaport Lane
Boston, MA  02210 -2019

Re: Cabot Corporation
 Form 10-K for the Year Ended September 30, 2012
Filed November 29, 2012
File No. 1 -5667

Dear Mr. Cordeiro :

We have reviewed your filing an d have the following comments.  In some of our
comments, we may ask you to provide us with information so we may better understand your
disclosure.

Please respond to this letter within ten business days by prov iding the requested
information  or by advising us when you will provide the requested response.   If you do not
believe our comments apply to your facts an d circumstances, please tell us why in your response.

After reviewing the information you provide in response to these  comments, we may
have  additional comments.

General

1. Where a comment below requests additional disclosures or other revisions to be made, please
show us in your supplemental response what the revisions will look like.  These revisions
should be included in your future filings, including your interim filings.

Item 7. Management’s Discussion and Analysis of Financial Con dition and Results of
Operations, page 31

Critical Accounting Policies, page 31

Goodwill and Long -Lived Assets, page 33

2. Please expand your disclosures to clarify the level at which you determine your reporting
units and describe how you determined them.   Specifically address if the businesses

Eduardo E. Cordeiro
Cabot Corporation
February 15, 2013
Page 2

 underlying your Performance Material and Advanced Technologies business segments are
reporting units.  Refer to ASC 350 -20-35-33 through 37 and ASC 350 -20-55-1 through 55 -9.

3. Please expand your disclosures regardi ng impairment of long -lived assets to address h ow you
group long -lived assets for impairment and your basis for that determination .

Results of Operations, page 38

Provision for Income Taxes, page 41

4. You disclose on page 38 that your non -GAAP measure “ operating tax rate ” exclude s discrete
tax items, which are unusual or infrequent items, and the impact of certain items on both
operating income and the tax provision.  Please reconcile your effective tax rate to your
operating tax rate and provide a  statement disclosing the reasons why management b elieves
that presentation of this  non-GAAP financial measure provides useful information to
investors .  Refer to Item 10(e)(1)(i)(A) and (B) of Regulation S -K.

Item 8. Financial Statements and Supplementary Data , page 54

Note M. Venezuela, page 83

5. We note that g iven the uncertainties around the convertibility of the Venezuelan bolivar to
the U.S. dollar and the ability of entities to actually repatriate U.S. dollars from Venezuela,
the Company has  endeavored, w henever possible, to repatriate the Company’s cash from its
Venezuelan subsidiaries using available mechanisms. Please tell us and clarify in future
filings whether the Company has been able to repatriate such cash during the periods
presented and, if so, quantify the amounts repatriated.

6. We note that  management has closely monitored its investment in the operating affiliate in
Venezuela to ensure that the investment continues to be recoverable  and that you still intend
to convert substantially all boliv ars held by its Venezuelan subsidiaries to U.S. dollars as
soon as practical .  In light of your recent ability or inability to repatriate cash from these
subsidiaries, please tell us and expand your disclosures in future filings to clarify how you
have det ermined that your investment is recoverable.

Note T. Commitments and Contingencies, page 102

7. We note your disclosure on page 103 that the $7 million reserve for environmental matters
represents your current best estimate of costs likely to be incurred for remediation.  If there is
at least a reasonable possibility that a loss exceeding amounts already recognized may have
been incurred for any of your environmental proceedings, please revise to either disclose an
estimate of the additional loss or range of loss, or state that such an estimate cannot be made.
If you have not disclosed an estimate because the amount is immaterial, please disclose that
fact in lieu of providing quantified amounts.  Please refer to ASC 450 -20-50.

Eduardo E. Cordeiro
Cabot Corporation
February 15, 2013
Page 3

Note V. Financial Informat ion by Segment & Geographic Area, page 106

8. You identify four business segments : Reinforcement Materials , Performan ce Materials,
Advanced Technologies,  and Purification Solutions.   Performance Material is comprised of
two businesses: Specialty Carbons and Compounds and Fumed Metal Oxides.  Advanced
Technologies is comprised of five businesses:  Inkjet Colorants, Aerogel, Security Materials,
Elastomer Composites and Specialty Fluids.  We have the following comments in this regard:
 Please tell us how you cons idered if these businesses are operating segments as defined
by ASC 280 -10-50;
 Please revise your accounting policy to clarify how you identified your operating
segments.   Specifically, please clarify the level at which your chief operating decision
maker (CODM) receives financial information for purposes of making decisions about
the allocation of resources and evaluating performance; and
 If you are aggregating any operating segments into reportable segments, please disclose
this fact in accordance with A SC 280 -10-50-21a and provide disclosures that confirm the
aggregated operating segments all have similar economic characteristics in addition to
similar products and services, processes, customers, distribution channels, and regulatory
environments.  Pleas e refer to ASC 280 -10-50-11 for guidance.

We urge all persons who are responsible for the accuracy and adequacy of the disclosure
in the filing to be certain that the filing includes the information the Securities Exchange Act of
1934 and all applicabl e Exchange Act rules require.   Since the company and its management are
in possession of all facts relating to a company’s disclosure, they are responsible for the accuracy
and adequacy of the disclosures they have made.

 In responding to our comments, please provide  a written statement from the company
acknowledging that:
 the company is responsible for the adequacy and accuracy of the disclosure in the filing;
 staff comments or changes to disclosure in response to staff comments do not foreclose
the Com mission from taking any action with respect to the filing; and
 the company may not assert staff comments as a defense in any proceeding initiated by
the Commission or any person under the federal securities laws of the United States.

You may contact Lisa Etheredge, Staff Accountant,  at (202) 551 -3424 or Jeanne Baker,
Assistant Chief Accountant,  at (202) 551 -3691 .

Sincerely,

 /s/ Rufus Decker

Rufus Decker
Accounting Branch Chief