Background and Objectives: PNH is a chronic hemolytic disease. Due to rarity and aB.S.ence of any clear statistical and epidemiologic information about this disease, the aim of this study was to evaluate the prevalence, and clinical or laboratory signs about PNH in patients that referred to Shiraz University of Medical Sciences.Materials and Methods: We reviewed 18 PNH-affected cases admitted in Namazee and Shahid Faghihi hospitals during 1977-2008. To evaluate patients' data, we designed a questionnaire that addressed demographic, clinical, and laboratory features, together with diagnosis and relevant treatment procedures.Results: Out of the patients, there were 11 male and 7 female all within the age range of 14-57 years.The most common clinical features were anemia and pallor in 17 patients (94.4%), jaundice in 10 (55.5%), aplastic anemia in 6 (33.3%), and vein thrombosis in 5 (27.7%). Pancytopenia was reported in 50% of patients. As far as the treatment procedures are concerned, the patients were shown to be treated with prednisolon, folic acid, danazol, iron and antiplatelet drugs. There were also 10 patients who recieved blood transfusion because of low Hb levels.Conclusions: PNH is a rare and chronic disease that should be considered in all patients with hemolytic anemia where other possiblities causes have been eliminated.