The age-specific rate of exposure to hepatitis A virus (HAV) was studied in 1015 native Saudi Arabians (504 males, 511 females) from the Riyadh area. The relatively high prevalence of antibody to HAV (anti-HAV) (38.6%) in children between 1 and 4 years of age indicates that infection is acquired early in life in the Saudi Arabian population. The prevalence of anti-HAV was found to increase steadily so that by the age of 30 years 91.0% of Saudi Arabians have anti-HAV. The prevalence in adult Saudi Arabians was compared with that in expatriates from various parts of the world working in Saudi Arabia. It was lowest among Swedish (10.7-12.3%) and highest among Yemeni (94.5%) blood donors while British blood donors were intermediate same among Saudi Arabian, Yemeni, Egyptian and Filipino blood donors (91.0-94.5%). All the donors tested were of the same age group (20-35 years).