T-tube drainage of the common bile duct (CBD) following duct exploration has become standard surgical practice. This randomized prospective study has compared primary closure versus T-tube drainage of the CBD following exploration for calculous disease. Thirty-seven patients underwent primary closure and 26 underwent closure over T-tube. Both groups were comparable in terms of age, indications for surgery, associated illnesses, pre-operative bilirubin, amylase and white cell count. Forty-three per cent of operations were performed by a consultant in the primary closure group and 65% in the T-tube group. There was no significant difference in the duration of operation, incidence of wound infection, surgical or other complications following operation between the two groups. However, the postoperative stay was significantly prolonged in the T-tube group, to a median of 11 days, compared to 8 days in the primary closure group (P = 0.0001). This prolongation in stay was unrelated to whether admission was as an emergency or elective. T-tube drainage of the bile continued for a median of 7 days postoperative, whereas the bile drained via a wound drain in only 13 (35%) of the primary closure group, for a median of 5 days in these 13 patients. Long-term follow up was achieved in 48 patients, by a questionnaire sent at a median of 2.8 years following operation. Abdominal pains following recovery from the operation were experienced by 18% of the primary closure group and 20% of the T-tube group. No patient developed jaundice or pancreatitis, nor needed further biliary surgery following operation.(ABSTRACT TRUNCATED AT 250 WORDS)