The number of neonates who undergo intracardiac repair for congenital heart disease has increased in recent years. In considering appropriate surgical options in such circumstances, normal values for various cardiovascular dimensions are needed. We measured 19 parameters for the heart and great arteries (four valves, pulmonary tree, aortic arch, ascending and descending aorta, ventricular septum, left ventricular internal and posterior wall dimensions) using cross-sectional echocardiography in 55 premature and full-term infants (ranging in gestational age from 23 to 41 weeks, in body weight from 543 to 3966 g). The increase in each dimension correlated closely with body weight (r=0.62 to 0.87) and was found to follow a linear regression. The diameter of the isthmus was found to be smaller, and the size of mitral valve annulus larger, than previously published values.