Collagen and gelatin containing biomaterials are relatively more susceptible to bacterial infection. Systemic administration or local delivery of antibiotics after implantation does not seem to solve the problem either effectively or easily. Antibiotics may be incorporated in the implant; but many, being water soluble, are quickly absorbed and not effective for adequate time periods. Resorcinol monoacetate (RMA) is a relatively water insoluble antibacterial agent which partially crosslinks collagen and has the potential to be an intrinsic antibiotic in collagenous bioprostheses. This study confirms the efficacy of RMA as a chemical that: (a) mildly crosslinks collagen at pH 3.5-4.5; (b) releases very slowly from the pretreated collagen sponge when washed in aqueous medium; (c) inhibits bacterial growth on the pretreated collagen sponges, at 2% (w/w) concentration, for at least 12 days; (d) remains biocompatible under treated conditions.