Atropine and glycopyrrolate combined with either methohexitone or thiopentone were compared with the induction agent alone in patients undergoing electroconvulsive therapy. Patients acted as their own controls in each sub-group defined by induction agent. Pupil size, muscle twitches, presence of hiccups and the extent of oropharyngeal secretions were noted. Methohexitone produced a greater and more prolonged increase in pupil size than did thiopentone. The subsequent pupil size following the atropine-methohexitone mixture was significantly greater than that following the glycopyrrolate-methohexitone mixture. The combination of atropine with thiopentone produced a greater "secondary" mydriasis than thiopentone alone, or thiopentone combined with glycopyrrolate. The effect of the glycopyrrolate-thiopentone combination did not differ significantly from that of thiopentone alone. Methohexitone was associated with a greater incidence of hiccups, muscle twitching and excessive salivation.