Sufficient echocardiographic analysis of premature infants has not yet been presented. Therefore echocardiograms of 105 babies without cardiovascular disease weighing 0.6--4.0 kg were analyzed. Normal data for right ventricular dimension, diastolic left ventricular inner dimension, left atrium, aorta, septums left ventricular posterior wall, cardiac depth, amplitude and closing velocity of the anterior mitral leaflet have been established. All measurements are a linear function of bodyweight with a very good correlation.