We designed this study in order to evaluate those cross-sectional echocardiographic projections of most value in the diagnosis of ventricular septal defects and to compare the techniques of cross-sectional and Doppler echocardiography in these lesions. We studied 71 cases with ventricular septal defects confirmed by cross-sectional and/or pulsed Doppler echocardiography. The defect was imaged by cross-sectional echocardiography in 49 patients but not imaged in 22. In the group of 49 patients, except two with pulmonary hypertension, pulsed Doppler enabled us to detect a left-to-right shunt at ventricular level. In the second group of 22 patients, a positive pulsed Doppler signal was detected in the ventricles although no defect was visualized. Pulsed Doppler examination supplemented the information detectable from cross-sectional echocardiography in small defects; in the diagnosis of multiple septal defects; in the presence of aortic valve regurgitation in doubly committed and subarterial defects; in those having residual shunts after surgical correction; and in those with tricuspid valve regurgitation in the setting of perimembranous defects. Continuous wave Doppler cannot always be reliably employed in the evaluation of transventricular pressure gradient because of a failure to align with the jet in the presence of poor signals. The sub-costal oblique projections and the introduction of the right oblique sub-costal view proved, in our hands, to be the most important tools for identifying and classifying the various types of ventricular septal defect.