13 patients with chronic granulocytic leukaemia (C.G.L.) which was unsatisfactorily controlled underwent splenectomy. 3 out of 4 patients with hypersplenism did well, as did 5 out of 8 patients in whom the C.G.L. had undergone metamorphosis to a refractory phase. In a case of C.G.L. complicated by severe myelofibrosis the need for transfusion was reduced but survival was short. Splenectomy should be considered when C.G.L. in its chronic phase is complicated by hypersplenism, and may be considered as a part of the treatment after C.G.L. has undergone metamorphosis to a refractory phase. However, a favourable outcome is unlikely for patients over 65 years, and in the presence of coexistent illnesses, rapidly progressive metamorphosis to an acute phase, or severe bone-marrow failure from any cause. In C.G.L., elective splenectomy early in the chronic phase must be clearly distinguished from splenectomy performed at a later stage when the disease is not well controlled.