A randomized clinical trial was undertaken to compare early and delayed cholecystectomy for acute cholecystitis. Patients entering early (n = 83) or delayed (n = 82) surgery groups were comparable with regard to prerandomization data. One patient in the early group and five in the delayed group refused surgery (p < 0.1) and two misdiagnoses occurred in each group. (2.4%). There was no difference in the incidence of technical difficulty measured by operative complications and duration of operations between the two groups. The same number of patients with common duct stones and perforations of the gallbladder were in each group. There was one death in the delayed group and none in the early group. Postoperative morbidity was 13.8% in the early group and 17.3% in the delayed surgery group (p > 0.1). Wound complications were slightly more common in the early surgery group (p > 0.1). In the delayed surgery group 13% of the patients had to be operated on before the planned date of surgery because conservative management failed. In addition, 15% of the patients had clear recurrent symptoms. Early surgery reduced total hospital stay by a mean of 7.5 days and the period of the patient's incapacity for work by 14.4 days. The data suggest that in acute cholecystitis early surgery is preferable when performed by an experienced surgeon with adequate pre- and intraoperative aids. Besides lower costs it offers the advantage of avoiding recurrent attacks and emergency operations without increasing mortality or morbidity.