Hepatitis B Virus (HBV) seric markers (HBs Ag, anti-HBs, and HBe Ag) were studied in 987 Senegalese leprosy patients (lepromatous: LL; tuberculoid: TT) in comparison with 6187 healthy adults (controls). Two populations of leprosy patients from ILAD (Institut de Léprologie Appliquée de Dakar) were studied: The First study (i.e.: study I) between 1973 and 1977 included 553 patients (329 LL; 224 TT). The Second study (i.e.: study II) between 1982 and 1986 included 434 patients (236 LL; 198 TT). HBV serological markers were tested by various techniques. By RIA, they were present in 98% and 96.5% in the studies I and II respectively. Each marker was studied and compared to the control population. HBs Ag detected by RIA was present in 25.5% (study I) and 23.0% (study II) when comparing to 15.2% in the control group. This marker was correlated with leprosy forms (LL and TT), age, sex, ethnic group.