Proplast, a new alloplastic material, was evaluated for use in head and neck reconstructive surgery. Soft tissue and bony responses were evaluated in four cats and six monkeys. Soft tissue implants were placed over the nasal bridge subperiosteally and subdermally. Bony responses were evaluated by obliterating the frontal sinuses and the mastoid cavities. In a nine-month follow-up period, it appeared that proplast was tolerated well in body tissue and integrated with the surrounding tissue by fibrous ingrowth that occurred within 30 days. There were no major undesirable side effects.