The authors conducted an investigation of the ocurrence of congenital transmission of Chagas' disease in a hospital for civil servants in the city of São Paulo. Four hundred ninety-two pregnant women were questioned on the possibility of having been infected by Trypanosoma cruzi. Twenty-two ofthem were considered by various criteria, as possibily infected. At the time of birth, cord blood was collected and afterwards tested for serological evidence of trypanosomal infection, including specific IgM antibodies. Five of the 22 samples tested gave positive results, none of them however, with positive IgM antibodies, not indicating transplacental passage of the parasite. The study did not demonstrate congenital infection, however it is a stimulus for similar investigations in areas of different endemicity of Chagas' disease and social and economical situation.