BACKGROUND We investigated the incidence of acute cholecystitis in patients with acute myeloid leukemia (AML) undergoing autologous bone marrow transplantation in complete remission. METHODS Thirty-five consecutive acute myeloid leukemia patients were given oral busulfan 4 mg/kg/day for 4 days and IV cyclophosphamide 50 mg/kg/day for 4 days followed by reinfusion of autologous bone marrow purged with 4-hydroperoxycyclophosphamide. RESULTS Five of 35 patients developed clinical evidence of acute cholecystitis, manifested by fever, nausea, vomiting, right-upper-quadrant pain, and abdominal guarding, within 18 days after autologous bone marrow infusion. Ultrasonography and CT scans of the abdomen supported the diagnosis of cholecystitis. Three patients underwent cholecystectomy, while two patients were treated medically; all recovered uneventfully. A review of 338 consecutive bone marrow transplant patients who underwent marrow transplantation for a variety of diseases and were treated with other high-dose cytotoxic regimens during the same time period revealed significantly fewer cases of cholecystitis, i.e. two, (p < 0.0001). CONCLUSIONS Five of 35 AML patients undergoing autologous bone marrow transplant using busulfan, cyclophosphamide, and purged bone marrow developed evidence of acute cholecystitis. These findings suggest that the busulfan/cyclophosphamide preparative regimen may be associated with acute cholecystitis. The true incidence of this injury and its pathogenesis remain to be elucidated.