Splenectomy in the chronic phase of chronic granulocytic leukemia was done in 32 patients, in 24 as part of a trial of elective splenectomy in early disease and in 8 because of thrombocytopenia preventing adequate therapy of the chronic phase. Patients with splenectomy had a median survival after diagnosis of 60 months. However, survival of patients operated on within 1 year of diagnosis was no different (median, 44 months) from that recorded in 120 consecutive Philadelphia chromosome-positive patients treated during the same time period (median, 42 months). After blastic transformation of disease, splenectomy patients survived slightly longer, responded more frequently to platelet transfusions, and avoided the morbidity of massive splenomegaly seen in 30% of patients treated with spleens retained. Response to blastic phase chemotherapy, however, was not improved. Prophylactic splenectomy in the chronic phase of disease did not influence survival but may ameliorate some complications of the terminal stages of illness.