Chemically purified bovine pericardial membrane, highly cross-linked with monomeric glutaraldehyde, was implanted in the TMJ area in ten adult rabbits in place of partially excised discs. Sham controls had the temporal aspect of the TMJ scraped with a scalpel. After 3 months, the whole TMJ area was processed for morphologic and scanning electron micrographic (SEM) evaluation. Evidence was found of the disintegration of the implanted pericardium, which was extensively infiltrated by inflammatory cells. The collagen matrix of the membrane was distended and dissociated, showing signs of degradation by its stainability with trichrome stain. It was concluded that cross-linking of a collagenous structure such as pericardium does not prevent it from being resorbed. It is suggested that the cytotoxic residues of polymeric glutaraldehyde within the implant may render the implant more resistant to cellular degradation.