In order to clarify the indications for splenectomy in patients with homozygous beta thalassaemia we studied, retrospectively, the basal pre-transfusion haemoglobin levels and blood transfusion requirements before and after splenectomy, in a series of patients with this disorder. Thirty-six patients, of whom 20 underwent splenectomy, were included in this study. Three groups of patients with homozygous beta thalassaemia were identified on the basis of clinical and laboratory findings. Two of the three groups consisted of 24 patients with beta thalassaemia major, subdivided retrospectively according to their response to splenectomy. The third group consisted of six patients with beta thalassaemia intermedia who had a comparably mild clinical course. In the first group of 16 patients with beta thalassemia major, monthly transfusions were required from the age of 6 months to 24 months and splenectomy resulted in temporary improvement for a period of 1-2 years. Thereafter, the transfusion requirements returned to pre-operative levels with no sustained improvements in base-line pretransfusion haemoglobin levels. Despite the fact that haematological improvement was temporary, it is felt that splenectomy is indicated in this group since the development and the general well-being of the children was significantly improved. In the second group of eight patients with beta thalassaemia major, transfusion requirements were relatively infrequent before 1-2 years, but after several years the transfusion requirement increased simultaneously with the development of 'hypersplenism'.