Two-dimensional and Doppler echocardiography has had a major impact on the diagnostic and therapeutic management of the newborn infant and fetus with a cardiovascular disorder. This article illustrates the use of the ultrasound techniques in the diagnosis of heart disease in the acyanotic newborn infant with a left-to-right shunt or ventricular outflow obstruction and the cyanotic infant with increased or decreased pulmonary vascularity. In addition, echocardiography has proven invaluable in the in utero diagnosis of cardiovascular abnormalities (structural or rhythm disturbances). This article also reviews the indications for and technical aspects of the fetal echocardiographic examination.