To characterize changes in circulation after birth, 11 normal full-term infants were examined with two-dimensional and pulsed Doppler echocardiography. The initial examination was performed within 10 hours after delivery and serially for 3 days. Retrograde diastolic pulmonary artery velocities, which are evidence for a patent ductus arteriosus, were detected in 10 infants (91%) on day 1, in 2 (18%) on day 2 and in none on day 3. Retrograde systolic descending aortic velocities, which are evidence of flow from the aorta into the ductus arteriosus, were observed in 10 infants (91%) on day 1, 9 (81%) on day 2 and 7 (64%) on day 3. Persistence of the retrograde systolic velocity in the descending aorta in the absence of retrograde diastolic velocity in the pulmonary artery is consistent with physiologic ductal closure beginning near the pulmonary artery end of the ductus arteriosus. Localized turbulent retrograde systolic flow, proximal to the septal leaflet of the tricuspid valve and consistent with tricuspid insufficiency, was detected in six patients (55%) on day 1, in eight (73%) on day 2 and in seven (64%) on day 3. Thus, tricuspid insufficiency appears to be a frequent observation in healthy newborns. Normal Doppler velocities in the great arteries and across the tricuspid and mitral valves of newborns up to 3 days of age are presented. These normal measures of intracardiac flow velocities may be used for comparison to identify abnormal flow profiles in newborns with congenital heart defects.