Two children were found to have cyclic thrombocytopenia, recurring at regular intervals. Coagulation studies as well as immunologic evaluation did not reveal any abnormality. One of the patients continued to demonstrate the cyclic fluctuation in platelet counts despite corticosteroid therapy and showed no response to fresh frozen plasma infusion. One patient had been previously misdiagnosed as having idiopathic thrombocytopenic purpura (ITP), which might have caused problems if other therapies had been tried. The diagnosis of cyclic thrombocytopenia led to appropriate counseling and activity regulation.