Past studies dealing with the vascular supply to surgically mobilized dentoalveolar segments have mentioned occasional encounters with vital root transection and have noted varying degrees of pulpal response to this insult. The purpose of this investigation was to observe the pulpal and periapical responses of monkey dental tissues to intentional vital root transection over a 1-year postoperative period. Four adult Macaca mulatta monkeys were used in this study. All roots were surgically transected within the apical third with a bur. Maxillary and mandibular quadrants for 1, 2, 3, 4, 6, 12, 24, and 52 weeks following surgery were obtained after the animals were killed by perfusion of the left ventricle. The tissue blocks were prepared by routine histologic methods. The results demonstrated a disruption of the normal pulpal architecture, with initial pulpal degeneration and subsequent early replacement by the periodontal ligament tissue. A cellular cemental lining of the root canal occurred in all specimens. The periodontal ligament-like tissue continued to deposit cementum, resulting in almost total obliteration of the root canal and pulp chamber and leaving an intact but much reduced blood supply to the pulp chamber containing periodontal tissues.