With 6,409 cases of AIDS recorded as at 31st March 1989, 130 of which were due to mother-to-foetus transmission, France is the European country most affected with HIV1 infection. From the results of a recent survey involving 40 p. 100 of all women who gave birth in continental France, the authors estimate that 0.05 p. 100 to 0.1 p. 100 of women delivered in 1988 were seropositive. HIV1 seroprevalence is about twice that figure in women at the beginning of pregnancy, since more than one-half of mothers who know they are seropositive choose to have their pregnancy interrupted. Investigations concerning the geographical origin and mode of contamination of seropositive women followed up in France showed that: (a) HIV1 infection is frequent in women who came from Zaire, Congo and the Ivory Coast and rare in women from Mali and Senegal. There was a similar contrast between women from Haiti and those from the French Antilles; (b) drug abuse plays a major role in the other seropositive women: 70 p. 100 were drug addict and 15 p. 100 had been contaminated by male drug addicts. Heterosexual contamination by multiple partners not classified as being at risk is exceptional, but it seems to be the rule in seropositive women from central Africa and Haiti. The authors emphasize the value, methods and indispensable extension of HIV1 seroepidemiological studies in pregnant women.