The outcome of patients with cholesterolosis was compared with that of those with chronic cholecystitis operated on for chronic acalculous biliary pain. A total of 55 patients with acalculous biliary pain with a median symptom duration of 24 (range 6-120) months were investigated by dynamic cholescintigraphy and followed for a median of 24 (range 12-60) months. Thirty-five patients underwent cholecystectomy, of whom 22 had a low gallbladder ejection fraction (under 35 per cent), with symptomatic improvement in 21 of these (P < 0.01). All four patients with a normal ejection fraction (35-50 per cent) improved after cholecystectomy but only four of nine with a high ejection fraction (over 50 per cent) did so. Results of histological examination were available in 32 patients and revealed cholesterolosis in 20. A low ejection fraction was found in 16 patients with cholesterolosis, of whom 15 showed symptomatic improvement after cholecystectomy; the other four patients had a high fraction and all improved after cholecystectomy. Overall, symptoms in 19 of 20 patients with cholesterolosis improved after cholecystectomy compared with only seven of 12 with chronic cholecystitis (P = 0.03).