**Exhibit10.19(f)**

December 13, 2006

Credit Suisse International

(formerly known as Credit Suisse First Boston International)

One Cabot Square

London E14 4QJ

England

Cephalon, Inc.

41 Moores Road

P.O. Box 4011

Frazer, Pennsylvania

19355

Ladies and Gentlemen,

Referenceis made to the warrant transaction (the“**Transaction**”) entered into by Credit Suisse International (“**Party A**”) and Cephalon Inc. (“**Party B**”) pursuant to an ISDA confirmation dated asof June 6, 2003 and with an Expiration Date of June 15, 2010  (the “**Confirmation**”).  Capitalized terms used herein withoutdefinition shall have the meanings assigned to them in the Confirmation.

Notwithstanding anything to the contrary in the Confirmationand the Agreement, Party A and Party B hereby agree that (i) the Transaction inrespect of 3,103,767 Warrants (the “**TerminatedPortion**”) shall be unwound as of December 13, 2006, (ii) theTransaction shall continue with respect to the remaining 3,533,401 Warrants and(iii) Party B shall deliver to Party A, in satisfaction of Party B’s paymentobligation with respect to the Terminated Portion, through the Agent, 940,504 Shareson the date that is the third business day following the date of this letter,subject to Party A’s election to set off its right to receive the Shareshereunder against any obligation Party A may have to deliver Shares under anyEquity Transaction that is terminated on the date hereof.  “**Equity Transaction**”means any transaction in Shares that qualifies as equity under applicableaccounting rules.

In addition, PartyB hereby represents and warrants to Party A that Party B is not, on the date hereof, aware of anymaterial nonpublic information concerning the Issuer or the Shares.

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Pleaseindicate your agreement with the terms set forth in this letter by signingbelow.

Sincerely Yours,

CREDIT SUISSE INTERNATIONAL (**Party A**)
|        | By:    | /s/ Martin Cox                          |
|--------|--------|-----------------------------------------|
|   | Name:  | Martin Cox                              |
|   | Title: | Vice President, Complex Product Support |
|   |   |                                    |
|   |   |                                    |
|   | By:    | /s/ Karen Quick                         |
|   | Name:  | Karen Quick                             |
|   | Title: | Vice President, Complex Product Support |

 

CREDIT SUISSESECURITIES (USA) LLC, acting through its New York branch and solely in itscapacity as Agent
|        | By:    | /s/ Melissa Garcia                            |
|--------|--------|-----------------------------------------------|
|   | Name:  | Melissa Garcia                                |
|   | Title: | Asst. Vice President, Complex Product Support |
|   |   |                                          |
|   |   |                                          |
|   | By:    | /s/ Anthony Fisher                            |
|   | Name:  | Anthony Fisher                                |
|   | Title: | Vice President, Complex Product Support       |

 

CEPHALON, INC. (**Party B**)
| By:    | /s/ J. Kevin Buchi                 |   |
|--------|------------------------------------|--------|
| Name:  | J. Kevin Buchi                     |   |
| Title: | Executive Vice President & CFO |   |
|   |                               |   |
|   |                               |   |
| By:    | /s/ Bryan Reasons                  |   |
| Name:  | Bryan Reasons                      |   |
| Title: | Vice President,  Risk Management   |   |

 

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