In a study carried out in Kampala, Uganda, among 570 parturient African women it was shown that 5.6% had infected peripheral blood and 16.1% had a placenta infected with malaria. The dominant infecting Plasmodium was P. falciparum. Only one case of congenital malaria was seen among the neonates.The average weight of 92 babies born from mothers with infected placentae was 263 g less that that of 478 babies born of non-infected mothers. This difference is statistically highly significant (P<0.001). The lowering of weight in the infected group was not affected by the sex of the neonate or by possible genetic differences. Primiparae had a higher frequency of infected placentae (21.7%) than the multiparous women (14.7%); this difference is attributed to the over-all younger age of these women.It is suggested that routine malarial prophylaxis should be considered for administration to pregnant women in endemic malarial areas.