The purpose of the present study was to evaluate independently the regeneration capacity of a reduced periodontium, and the potential for new connective tissue attachment to a periodontally exposed root surface. A reduced periodontium was produced around a maxillary central incisor in two Rhesus monkeys using orthodontic elastics. The regeneration capacity of this reduced peridontium was investigated by extracting the periodontally involved tooth and transplanting into the socket the contralateral incisor which had a normal periodontium. The potential for new connective tissue attachment to a periodontally exposed root surface was evaluated by transplanting an exposed root into a normal periodontium. These exposed roots were the incisors extracted from the reduced peridontium. Control specimens were obtained by extracting and reimplanting or transplanting the remaining maxillary and mandibular incisors. Forty days after the experimental procedures, block sections were removed and prepared for histologic analysis. The exposed root surface that had been put into the normal periodontium was lined with epithelium interposed between root surface and alveolar bone. The normal root surface that had been put into the reduced periodontium had connective tissue reattachment in the periodontal ligament and supracrestal regions. Areas of ankylosis and root resorption were present in all specimens, as was new cementum in the periodontal ligament region. The results indicated that root surface alterations, rather than presence of a reduced periodontium, inhibited new connective tissue attachment.