We have undertaken a prospective, randomized study to determine the incidence of postoperative nausea and vomiting during intensive care stay after cardiac surgery, and to study the effect of addition of droperidol to an infusion of morphine used for postoperative analgesia. Data from 398 patients were examined. The use of droperidol reduced complaints of nausea from 92 of 198 (46.5%) to 46 of 200 (23%) and episodes of retching or vomiting from 73 of 198 (36.9%) to 44 of 200 (22%). The number of patients requiring rescue antiemetic medication was also reduced significantly from 100 of 198 (50.5%) of those who did not receive droperidol to 44 of 200 (22%) of those given droperidol. Mean duration of intubation was 4.9 h and was unaffected by the use of droperidol. Droperidol had no effect on mean length of stay in the recovery unit.