Congenital malaria is defined as the presence of Plasmodium parasites in the erythrocytes of newborns less than seven days old. The aim of this study was to determine the incidence of congenital malaria and its possible clinical consequences. We carried out a prospective survey in Niamey, the capital of Niger (600,000 inhabitants) from July to September 1993. Niamey is in an area of mesoendemic malaria and this period of the year corresponds to the rainy season, when malaria transmission is maximal. Ninety mothers and their newborns were included. We assessed the clinical status of the mother and child at the time of the delivery, and took blood smears to check for parasitemia and blood samples to check for antimalaria antibodies by indirect immunofluorescence (IIF). The placenta was not examined. Clinical signs of malaria (fever, splenomegaly, anemia and jaundice) were absent in all mothers and children and 88 of the 90 children had normal birth weights. Plasmodium falciparum was the only parasite detected, with 49 of the 90 mothers and 12 of the 90 newborns having positive blood smears. Serological tests detected the presence of antimalaria antibodies in 73 of the 90 mothers (81.1%) and 68 of the 90 newborns (75.5%). Thus, we found no cases of congenital malaria with clinical signs in this study, despite the high frequency of parasites and antimalaria antibodies. The reasons for this absence of cases of congenital malaria with symptoms are discussed.