Anatomopathological studies were performed in 15 placentas of pregnant women who were seropositive for Chagas' disease. Nests of Trypanosoma cruzi amastigote s were found in the placenta and umbilical cord of three of them (20 percent). The parasitism was extensive in two of the cases, where the nests were predominantly located in the umbilical cord and in the chorionic plate. No significant macroscopically difference was observed between the infected and the not infected placenta. However, the two more severe cases showed focal histological lesions with destruction of the trophoblastic epithelium, and inflammatory reactions which have not been observed in uninfected or slightly infected placentas. These changes would be related with the intensity of the fetal parasitism in congenital Chagas'disease