The epidemiologic features of HBV, HDV and HIV in the general population of Hamadan province of Iran were studied. A total of 4930 subjects (1649 males and 3281 females) constituted the study population.Seropositivity for any HBV marker was found in 25.72 % of the subjects. Of these, 2.49 % were carriers of HBsAg, 18.09% were positive for anti-HBs and 5.13 % for anti-HBc alone. HBeAg, anti-HBC IgM, and anti-HDV were present in 13.8, 6.5 and 2.4% of HBSAg carriers, respectively.Antibody to HIV was detected in none of the 4930 sera tested.Prevalence of HBV infection was lowest in children and young adults < 19 years and highest in adults > 60 years. No significant difference was observed between the rates in males and females. Family size and prevalence of HBV infection were unrelated but an inverse relation was found between HBV infection and education. Unmarried men and women showed the lowest (18.26%) and widows and divorcees the highest (51.59 %) rate of HBV infection.Our results suggest that horizontal transmission is likely to be the primary mode of acquisition of HBV infection in children and young adults. Also infection is partly transmitted before or soon after birth to babies of HBsAg-carrier mothers.Socioeconomic and demographic variables have a greater impact on the prevalence of HBV infection than blood or medical care variables in our population.