One hundred and eighteen patients in whom postoperative gastrointestinal atony had lasted for 48-72 hours, were given one or two intravenous injections of different doses of cisapride (2, 4 or 8 mg), or vehicle. The first occurrence of flatus was taken to mark the cessation of ileus. There was no significant difference in remission of ileus between the groups in the first hour following injection. All patients not responding to treatment in the first hour were given a repeat dosage and observed for the following 3 hours. Among this group, there was a significant remission of ileus in patients who had received 2 X 8 mg, which was particularly marked in those who had undergone intraperitoneal surgery. This study suggests that cisapride in repeated dosage may be of value in inducing remission in prolonged surgical ileus, particularly in patients who have undergone intraperitoneal operations.