Several workers reported an increased susceptibility to hepatitis B virus (HBV) in immunosuppressed patients. A study was carried out on 4 groups of supposedly immunocompromised patients for hepatitis B surface antigen (HBsAg), and anti-HBs. The 4 groups of patients were suffering from: Leprosy, Bronchial asthma, Diabetes and hepatosplenic Schistosomiasis. Serum specimens were obtained from 137 patients representing the 4 groups and from a control group of 25 healthy individuals. All sera were tested by ELISA technique for HBsAg and anti-HBs. Results indicated that HBsAg carrier rate was 4% for the control healthy group, 7% for Bronchial asthma, 10% for Diabetes, 24% for Leprosy and 28% for hepatosplenic Schistosomiasis. On the other hand, the anti-HBs was 21% for the control group, 29% for Schistosomiasis, 55% and 58% for Diabetes and Bronchial asthma respectively and 74% for Leprosy. This study shows that immunosuppressed patients particularly those suffering from leprosy and hepatosplenic Schistosomiasis experience higher HBsAg carrier rate than the control group for the endemic hepatitis B (6-7 times higher for leprosy and Schistosomiasis). An important observation was the diminished anti-HBs rate in hepatosplenic Schistosomiasis patients, despite the highest HBsAg carrier rate they exhibited. This may be due to an immunological defect, resulting in an unsatisfactory antibody response and chronic hepatitis B antigenemia. In Egypt, where Schistosomiasis is prevalent (40-50%), the problems caused by hepatitis B infection are increased.