The case of a patient with cyclic, acquired, periodically amegakaryocytic thrombocytopenia is described. On the base of a seemingly typical megakaryocytic thrombocytopenia ITP was diagnosed at first. He did not respond to steroid, therefore splenectomy was performed. He relapsed and thereafter severe thrombocytopenia was observed, periodically, for 8-10 days in every five-six weeks. During the cytopenic periods recognizable megakaryocytes and precursors were totally absent from the bone marrow. After the haemorrhagic periods platelet counts elevated to normal or even higher levels and the marrow was plenty of megakaryocytes. Vincristine was unsuccessful, but cyclosporine administration for a longer time was not without success. The patient has a normal platelet count since one year. No similar case of cyclic amegakaryocytic thrombocytopenia was found in the literature.