The prevalence of hepatitis B virus (HBV) serological markers was determined in a prospective fashion by radioimmunoassay in 2,084 healthy volunteer blood donors. The results showed that 51.2% of the donors were positive for at least one marker, and the percentage of occurrence of each marker was: HBsAg 5.3, anti-HBs alone 1.7, anti-HBc alone 10.8, anti-HBs and anti-HBc 33.3. Because of the size of the problem this investigation strongly demands further studies on the potential role of blood positive for anti-HBc in transmitting HBV infection in our geographical area.