an antigen delivery system utilizing a biodegradable polymer with good mechanical properties in combination with a material stimulating the immune system . the material having adjuvant activity may be polymer degradation products or an adjuvant which is contained within or bound to the polymer . in one embodiment , the polymer is formed from tyrosine dipeptides . poly is a preferred tyrosine dipeptide polymer for constructing implantable delivery systems for antigenic material . the polymer is not an adjuvant in itself but degrades into products which stimulate the immune system . the tyrosine dipeptide can also be used as a conventional adjuvant . the advantages of the system are that a polymer can be used to form a biodegradable integral structure which is useful as both an implantable source of an antigen or other biologically active compound and as a control means for the rate of release of the biologically active compound , wherein the result is sustained , relatively constant delivery of antigen with simultaneous stimulation of the immune response .