Exhibit 18.1

                 Preferability Letter from Arthur Andersen LLP

Cephalon, Inc.

Re: Form 10-Q Report for the quarter ended March 31, 2002

Gentlemen/Ladies:

This letter is written to meet the requirements of Regulation S-K calling for a
letter from a registrant's independent accountants whenever there has been a
change in accounting principle or practice.

We have been informed that, as of January 1, 2002, the Company changed from the
FIFO method of accounting for inventory to the LIFO method. According to the
management of the Company, this change was made to provide a better matching of
revenues and expenses.

A complete coordinated set of financial and reporting standards for determining
the preferability of accounting principles among acceptable alternative
principles has not been established by the accounting profession. Thus, we
cannot make an objective determination of whether the change in accounting
described in the preceding paragraph is to a preferable method. However, we have
reviewed the pertinent factors including those related to financial reporting in
this particular case on a subjective basis, and our opinion stated below is
based on our determination made in this manner.

We are of the opinion that the Company's change in method of accounting is to an
acceptable alternative method of accounting, which, based upon the reasons
stated for the change and our discussions with you, is also preferable under the
circumstances in this particular case. In arriving at this opinion, we have
relied on the business judgment and business planning of your management.

We have not audited the application of this change to the financial statements
of any period subsequent to December 31, 2001. Further, we have not examined and
do not express any opinion with respect to your financial statements for the
quarter ended March 31, 2002.

Very truly yours,

/s/  Arthur Andersen LLP