Although thrombocytosis is a very common finding after splenectomy, the thromboembolic risk of postsplenectomy thrombocytosis has not been clarified. To our knowledge, this retrospective study of 318 patients without myeloproliferative disorders who underwent splenectomy is the largest of its type. Thrombocytosis developed in 75% of the patients. No substantial increase in the incidence of thromboembolism was detected in patients with thrombocytosis.