To ascertain whether maternal infection with Trypanosoma cruzi may influence the course of the parasitic infection in offspring, two groups of female 1 rats were mated with syngeneic sires. One group of females was infected with 10(6) trypomastigotes of T. cruzi three times at weekly intervals. All offspring were nursed by their mothers until weaning and then separated into two groups of young, one to be infected with the same dose of T. cruzi, and the other to remain uninfected. Infection of pregnant rats caused no aggravated disease but resulted in a self-controlled infection that did not cause any deaths or affect their reproductive capacity. The number of young delivered, litter size, fertility coefficient, and offspring weights at weaning were also unaffected by maternal infection; however, the survival coefficient decreased in comparison with values recorded in the offspring of uninfected mothers. The latter finding is likely due to neonatal transmission, since bloodstream forms of T. cruzi were observed in a few offspring of infected mothers. While infected offspring whose mothers had been inoculated with T. cruzi during pregnancy were not protected from acute infection, the occurrence of chronic focal myocarditis was less prevalent when compared with that recorded in chronically infected offspring born to uninfected mothers.