A case of polycythemia vera, first diagnosed in a nine year old girl, is presented. The increase in red cell count, hematocrit and hemoglobin values was accompanied by an increase in total blood volume and true red cell volume. No other condition reported to be accompanied by polycythemia was found. Specific, mild deficiencies in certain coagulation factors were found. Iron kinetic study with Fe59 showed increased hemoglobin formation within normal iron pathways which is characteristic of polycythemia vera.