The relative prevalence of hepatitis B surface antigen (HBsAg), anti-HBs, and anti-hepatitis B virus core antigen (HBc), as markers of hepatitis B virus infection, among 1,866 apparently healthy residents of two Egyptian provinces representing Upper and Lower Egypt populations was determined using solid-phase radioimmunoassay (SPRIA). The prevalence rate of HBsAg in the Egyptian population was moderately high (10.1%); it was higher in the Upper Egypt (11.7%) than the Lower Egypt (8.0%) population and more frequent in young adults--especially those of Upper Egypt--and males than females in both populations. The prevalence of anti-HBs gradually increased with age; it was higher in the Lower Egypt (51.1%) than the Upper Egypt (41.7%) population, and it was higher in females than males. A remarkably high infection rate, as shown by the prevalence of anti-HBc, was found in both populations (88.0%), with minor variations depending on age, sex, and geographic area.