The value of 2D echocardiography was assessed prospectively in 82 patients (average age 2.6 months) including 41 newborn babies, in the emergency investigation of cardiac distress. The recording was made before any other investigations or treatment and associated subcostal and supra sternal views, and the results were compared with angiography (64 cases) or anatomical findings (44 cases). A cardiac abnormality was excluded in 5 cyanotic newborn children (persistent foetal circulation) and a precise diagnosis was made in 74 of the remaining 77 patients (94 p. 100). All cases of malposition of the great vessels were recognised (17 cases). The diagnosis was based on the simultaneous recording of the vessels, proximal branches and their ventricular connections. In conditions with severe obstruction of the pulmonary outflow tract (26 cases), 2D echo enabled an exact evaluation of ventriculo arterial concordance, pulmonary confluence and a quantitative assessment of the diameter of the pulmonary artery in 25 patients. Angiography provided little further information, mainly concerning associated lesions (anterior muscular VSDs, abnormalities of the supra aortic vessels). On the other hand, 2D echocardiography was superior to angiocardiography for the study of the atrioventricular values and intracavitary and subvalvular obstruction. 2D echo is a reliable method for emergency assessment of the indication for therapeutic catheterisation (atrioseptostomy). In other cases it allows it to be deferred and guided. The comparison of the results of 2D echo and angiocardiography in this series suggests the possibility of reducing the number of endocavitary investigations in the newborn and infant in the future, even in cases where surgery is being considered.