Congenital toxoplasmosis is potentially fatal for the fetus. During pregnancy, a mother can become infected by eating undercooked meat containing parasites (cysts), poorly washed raw vegetables (oocysts), or by ingesting oocysts present on contaminated hands. Prevention of congenital toxoplasmosis in France requires seronegative pregnant women to undergo serological monitoring from the time of pregnancy registration until delivery. In France, the prevalence of toxoplasmosis among pregnant women was 54.3% in the 1995 National Perinatal Survey (ENP 1995). During the ENP 2003, socioeconomic variables, as well as serological status (IgG and IgM) for toxoplasmosis, among all women who completed a pregnancy in France, were collected—along with other variables not specific to toxoplasmosis—over a one-week period in October 2003. The sample size in 2003 was 15,108 pregnant women, with a prevalence of toxoplasmosis of 43.8% [43.0–44.6]. Prevalence increased with age and varied by geographic region. It was high in the Southwest, the Paris region, and the overseas departments (DOM), and low in the Northeast. Prevalence was lower in colder geographic areas (departments where the number of days with temperatures at or below -5°C was higher). In 2003, as in 1995, prevalence increased with educational level, household employment status, and number of pregnancies. Among women of French nationality, prevalence fell by 21% between 1995 and 2003. This decline is more pronounced among women under 30 (26%) than among older women (17%). Despite a decrease in the prevalence of toxoplasmosis, it remains higher than in Northern European countries. If this decline continues, a reassessment of the relevance of the prevention program could be considered. It should be noted, however, that more than one in two women is likely to become infected during pregnancy. For this reason, it is important to effectively promote the preventive measures to be followed during pregnancy and to ensure that messages are properly disseminated and understood by pregnant women. (R.A.)