Between 1972 and 1985, 107 patients with chronic Idiopathic Thrombocytopenic Purpura underwent splenectomy. Platelet life span and sites of sequestration were studied with labelled platelets and external scanning. Medical treatment was always of scarce and transient effectiveness and had considerable side effects. Splenectomy had minimal complications and mortality and caused no hazard of overwhelming sepsis in adults. The results of splenectomy were very satisfying, especially when platelet sequestration was mainly splenic (remission in about 90% of patients). Surgical treatment is at present the most effective in patients with chronic ITP.