The seroepidemiology of infection due to rubella virus in Saudi Arabia was investigated in various age groups including unvaccinated children (newborn to 15 years of age) using a newer rubella antibody test system, the ELISA with maximum sensitivity and reliability. The assessment of the immune status indicated the lowest level of naturally acquired rubella IgG antibodies in children aged 13-18 months and thereafter a pattern of progressive age-specific increase in seropositivity. About 90 per cent of the women of childbearing age were seroimmune. The target population for rubella immunization is identified.