1 EXHIBIT 23.1 CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS We consent to the incorporation by reference in the Registration Statements (Forms S-8 Nos. 33-65224, 33-50116, 33-50114, and 33-96318) pertaining to the Employee Stock Purchase Plan, Outside Directors Stock Option Plan and 1991 Stock Option Plan of Protein Design Labs, Inc.of our report dated February 3, 1998 with respect to the financial statements of Protein Design Labs, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 1997. ERNST & YOUNG LLP Palo Alto, California March 30, 1998