Eighty-six patients with Down Syndrome were studied with the main purpose of quantifying the incidence of congenital heart defects and the risk of occurrence according to the mother's age. Thirty-eight patients had the cariotypes determined, 35 of them having trissomy of chromosome 21 and translocation in 3 cases. Congenital heart disease was found in 44 (51%) of the patients, the most common one being ventricular septal defect. An important incidence of Fallot's tetralogy was also found (20%). These 86 children were submited to 41 surgical procedures, most of them on the cardiovascular system. The maternal mean age was 33 ± 8.6 years and the estimated risk of Down Syndrome was 1/590, a lower value than the one reported in other studies.