Seventy-eight patients with perforated duodenal ulcer were prospectively studied between 1977 and 1982. Patients were alternately allocated to receive simple closure (Group I, 33 patients) and definitive surgery (Group II, 32 patients). High-risk patients and those whose conditions dictated a definitive operation were excluded. All patients in Group II had a truncal vagotomy and drainage except one who had a proximal gastric vagotomy. There was no death in Group I or Group II; the complication rate and postoperative course were similar. Twenty-seven patients in Group I and 26 patients in Group II were available for follow-up 12 to 80 months after operation, mean 39 months. Good/excellent results were achieved in 30 per cent of Group I compared with 81 per cent of Group II (P less than 0.01). Eighty-five per cent of Group I patients developed recurrent ulcer symptoms and 33 per cent had already had a second definitive operation. Two patients (8 per cent) in Group II were reoperated upon for recurrent ulcer due to an incomplete vagotomy. In a population of patients where long-term follow-up and medical treatment for duodenal ulcer is unsatisfactory, truncal vagotomy with drainage should be the treatment of choice for perforation. Simple closure should be reserved for high-risk patients or when the surgeon is inexperienced.