Splenectomy was performed in 45 patients with chronic myelogenous leukemia; 23 were in the chronic phase and 22 in the acute phase. Indications for operation included inability to control the disease by chemotherapy or radiation therapy, severe thrombocytopenia, frequent need for blood transfusion and extensive splenomegaly causing discomfort. Median survival time for these patients was better than survival time of other reported groups of patients who did not have a splenectomy. According to our criteria, splenectomy was beneficial to 15 patients in the chronic phase as well as to eight in the acute phase of chronic myelogenous leukemia. Median survival time after splenectomy was higher in patients who had splenectomy within two years of the diagnosis as compared with those who had the operation after two years. Splenectomy did not prevent the future onset of fatal blastic crisis. Although significant abnormalities in coagulation studies were seen in 37 of the patients, intraoperative hemorrhage was not a major problem. Considering the poor general condition, inadequate healing and susceptibility to infection, the postoperative mortality and complication rates were comparable with those reported in series in which splenectomy was performed for other diseases. It seems that splenectomy benefits a selected group of patients with chronic myelogenous leukemia; however, a randomized series would furnish better data upon which to make decisions.