Abstract: A prospective study was planned to determine the prevalence of anti-rubella antibody in female of reproductive age in Karachi to eliminate rubella virus infection to prevent CRS (Congenital Rubella Syndrome) by evaluating the importance of immunization of infants and susceptible females. About 1,225 women, referred to Dr. Ehsanullah`s Laboratory Karachi, during year 1999 to 2004 from various maternity homes for antenatal checkup, were included in this study. Rubella IgG antibodies determined by Enzyme Linked Immuno Sorbent Assay (ELISA). About 81% pregnant women were found to be seropositive by clinical or subclinical rubella infection/immunization (immune group) and 18% of pregnant women were seronegative for Rubella antibody of the I gG class with high risk of CRS (susceptible group), which can be reduced or eliminated by immunization programme for infants and adult females before marriages.