The effect of cholecystectomy on oesophageal function was examined prospectively. Of 37 patients studied, 17 (46 per cent) were still symptomatic 3-4 months after surgery. Thirteen patients (35 per cent) had abnormal oesophageal pH profiles before cholecystectomy, increasing to 27 (73 per cent) afterwards (P < 0.002). The mean (s.e.m.) DeMeester acid reflux score increased from 15.2(2.1) to 34.2(5.2) (P < 0.001) after operation. Lower oesophageal sphincter function, as measured by the sphincter function index, was significantly reduced in the patients with abnormal pH profiles after operation (P < 0.01). Mean(s.e.m.) supine gastric alkaline shift (proportion of time at pH > 4) increased from 9.2(2.0) to 17.7(3.7) per cent (P < 0.02) and the incidence of gastritis from eight patients (22 per cent) to 23 (62 per cent) (P < 0.001). These data suggest that cholecystectomy results in gastro-oesophageal reflux that appears to be related to compromised sphincter competence.