This is the first report of a congenitally transmitted case of Chagas disease occurring in Mexico, in a febrile premature newborn girl with low birth weight, hepatosplenomegaly and pneumonitis. Trypanosoma cruzi blood infection was detected using both direct smears and concentrated blood preparations. The patient's mother had a positive serological reaction by two techniques for anti-T. Cruzi antibodies. Two years after anti-chagastic treatment, the child has had a normal evolution, her serology is negative, and no abnormalities have been detected by electrocardiography.