Ashland 10-K 2011 FY Annual report

Exhibit 18

November 23, 2011

Board of Directors of

Ashland Inc.

50 E. RiverCenter Boulevard

Covington, Kentucky  41012-0391

Dear Directors:

We are providing this letter to you for inclusion as an exhibit to your Form 10-K filing pursuant to Item 601 of Regulation S-K.

We have audited the consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended September 30, 2011 and issued our report thereon dated November 23, 2011.  Note A to the consolidated financial statements describes changes in accounting principles for pension and other post-retirement benefit obligations and inventory costing.  It should be understood that the preferability of one acceptable method of accounting over another for pension and other post-retirement benefit obligations and inventory costing has not been addressed in any authoritative accounting literature, and in expressing our concurrence below we have relied on management’s determination that these changes in accounting principles are preferable.  Based on our reading of management’s stated reasons and justification for these changes in accounting principles in the Form 10-K, and our discussions with management as to their judgment about the relevant business planning factors relating to these changes, we concur with management that such changes represent, in the Company’s circumstances, the adoption of preferable accounting principles in conformity with Accounting Standards Codification 250, Accounting Changes and Error Corrections.

Very truly yours,

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP

Cincinnati, Ohio