Homologous tooth transplants evoke immunogenic rejection against antigens within donor periodontal ligaments cells and ground substance. Eight maxillary incisors of 6 juvenile animals were extracted, crowns and pulps removed by gutta percha; the roots were incubated serially in enzyme solutions and glutaraldehyde at 37 degrees C for 5 h to destroy cells, glycoproteins and proteoglycans. Seven control teeth from the same 6 animals were incubated in saline at 37 degrees C for 15 min. All teeth were then speedily transplanted to other animals which were killed at 6 wk or 3 months. Radiographs and histologic sections revealed extensive resorption and inflammation of all control teeth. Enzyme-treated teeth showed less inflammation with resorption mostly on the surface of the cut coronal dentine. A loose fibrous attachment usually formed on most aspects of the root surface with deposition of new cellular cementum within the donor ligament. Inflammation, where present, may have resulted from incomplete removal of periodontal ligament cells, ground substance, or from salivary bacterial contamination.