Isoflurane 0.5% in oxygen for conscious sedation was compared with placebo (oxygen) and with an equipotent concentration of nitrous oxide in oxygen, in patients scheduled for surgical removal of bilateral, similarly impacted lower third molars. The majority of patients were sedated with 0.5% isoflurane in oxygen and preferred it to both placebo and nitrous oxide in oxygen. It produced good operating conditions with cooperative patients and had no significant effect on vital signs. There were no significant intra- or postoperative adverse effects. Patients were street fit within 10 minutes after the end of the operation.