The traditional management of acute cholecystitis is initial conservative treatment with antibiotics followed by elective cholecystectomy. Although early cholecystectomy has often been advocated, there has been only one randomized controlled clinical trial comparing the two methods of treatment. This paper reports the preliminary results of such a trial in which 32 patients have been studied so far. Of the 17 patients managed conservatively, there was a misdiagnosis in 2 (11-8 per cent). In the remaining 15 patients with acute cholecystitis 3 (20 per cent) required urgent operation because of failure of medical treatment. Elective cholecystectomy was not technically difficult. Of the 15 patients treated by early cholecystectomy, there was a misdiagnosis in 1 (6-8 per cent). Surgery was technically difficult in 2 patients but cholecystectomy was possible in all. The former 2 patients required blood transfusion, but in the remainder the estimated blood loss was only slightly more than in the elective group. There was no mortality in either group nor any complication directly attributable to the biliary surgery. The incidence of minor postoperative complications was only slightly greater in those treated by early operation. The length of postoperative stay was similar in both groups but those treated conservatively spent an average of 11 more days in hospital. The preliminary results indicate that those treated by early cholecystectomy spend less time in hospital and avoid the complications of failed conservative treatment without the added risk of increased postoperative mortality and major complications.