The effect of acumpuncture on the pain perception threshold of maxillary incisors and canines as determined by a Bofors Pulp Tester was studied in 33 dental students 19-30 years of age. Test teeth were cleaned with pumice and 10% alcohol, air-dried, and insulated at the approximal surfaces with strips of rubber dam. Based on a comparison of bipolar and monopolar stimulation the latter method was chosen, with the cathode placed on the incisal third of the facial surface, the indifferent electrode in the subject's hand. In separate groups of subjects thresholds were assessed four times at intervals of 15 min without acupuncture (1), with acupuncture performed manually (2) and electrically (3), and during electrical stimulation with surface electrodes over acupuncture points (4). On separate days acupuncture and surface stimulation was applied unilaterally at the points S2 (cheek), Li4 (hand), or S44 (foot). Compared with control threshold (8.44 muA) acupuncture was accompanied by a small increase, most pronounced after 45 min (1.51 muA, P less than 0.0005). However, the hypalgesia observed was insufficient to justify acupuncture as a means of pain control in conservative dentistry.