The aim of our study was to assess the serologic immunity to cytomegalovirus (CMV) in a population of pregnant women in Israel. We measured the titers of both IgG and IgM to CMV in 6,126 pregnant women by enzyme immunoassay. Of these, 84.3% were found to be positive for anti-CMV IgG and 15.7% were seronegative, and thus susceptible to primary infection. The total number of women positive for anti-CMV IgM, and hence suspected of being infected with the virus during or shortly before their pregnancy, was 43 (0.7%). An acute infection was therefore diagnosed in 4.35% of IgG seronegative women. A significantly higher CMV seropositivity rate was found in the parturient population as compared to surveys conducted in Israel in the 1970's. The seropositivity rates found in Israel are similar to those reported in Asia and Africa. The rate of serosusceptibility and the risk of primary CMV infection in pregnancy are lower in Israel than in Europe and North America. According to the observed incidence of primary CMV infection in pregnant women, it can be estimated that approximately 280 cases of fetal infection occur in Israel every year, potentially resulting in 56 symptomatic newborns.