Congenital heart diseases have been studied much more extensively in children than in neonates. In this study, we report on the findings from 57 neonates seen from June of 1995 through June 1996 in the nursery of a large public hospital in Belém, Para, Brazil. All were routinely examined by a paediatrician just after birth, and, when indicated, these babies were referred to the cardiology unit of our Hospital for assessment by a paediatric cardiologist. Most of the diagnoses were made by means of Doppler and cross-sectional echocardiography with color flow mapping. Several abnormalities of the cardiovascular system were diagnosed. The most frequent was patency of the arterial duct. But, since many ducts closed spontaneously, ventricular septal defect was the most frequent lesion seen even in the nursery. Four defects (patent arterial duct, ventricular septal defect, atrial septal defect and pulmonary stenosis) together accounted for two thirds of all cardiac abnormalities. Associated non-cardiac anomalies were more frequent in those with simple lesions within the heart. All the babies with complex heart disease, and the majority of those designated as having significant lesions, died before they could be discharged. Several risk factors were investigated. Among maternal drugs, misoprostol emerged as having a possible teratogenic effect.