We have developed methods for controlling the release of antibodies (Ab) from biocompatible polymers. Human Ab, human Ab fragments, and mouse monoclonal antibody (mAb) directed against human chorionic gonadotropin (anti-hCG) were incorporated into matrices of poly(ethylene-co-vinyl acetate), which is stable in biological environments. Human Ab and bovine gamma-globulin were also incorporated in biodegradable matrices of a poly-anhydride copolymer composed of a stearic acid dimer and sebacic acid. Abs were slowly released from all the polymeric carriers during 30 days of continuous immersion in buffered saline. The ability of anti-hCG to bind antigen was retained following release from EVAc matrices. Only minor Ab aggregation was observed following release from either polymer. Polymeric delivery systems, similar to those described here, may become an important element in the delivery of mAbs to humans for immunoprotection against infectious diseases or the delivery of mAb-conjugates for immunotherapy against cancer.