SummaryA new case of primary hemorrhagic thrombocythemia is presented, in which ferrokinetic studies were performed 3 times in different phases of the illness.The 84 years old patient fitted all the clinical and hematological criteria of these disease : repeated spontaneous hemorrhages, splenomegaly, persistent thrombocythemia, severe and prolonged anemia, leukocytes not in excess of 50.000 and a rich bone marrow with pronounced megakaryocytic preponderance.Radioactive phosporous treatment produced several remissions, but the patient died 2 years after the diagnosis was established, showing a transformation to acute monocytic leukemia.The quantitative determinations of iron kinetics in the hemorrhagic phase, in remission and in hematologic relapse showed an highly increased erythropoiesis despite of the existent anemia and an important ineffective erythropoiesis.Therefore, the authors feel that primary hemorrhagic thrombocythemia is a myeloproliferative disorder with a predominant platelet elevation.