Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon hematologic disease characterized by an abnormal sensitivity of blood cells to the lytic action of serum complement. We experienced one case of PNH in Yeungnam University Hospital from May 1983 to May 1989. The patients was followed up without severe complications for 4 years since diagnosis with the only consevating treatments such as washed blood transfusion, adrenal corticosteroids, androgens, folate and iron preparation, intermittently.