Two-dimensional echocardiography and color Doppler examinations were performed in 53 patients with 58 ventricular septal defects (VSD) proven surgically or anatomically. All patients also had angiocardiograms. Two-dimensional echocardiography/color Doppler examination detected all VSDs and correctly categorized the site and extension of VSDs in 50 of 58 (86%). All 40 perimembranous VSDs were diagnosed in the left ventricular outflow tract short-axis plane as an area of discontinuity adjacent to septal tricuspid valve leaflet attachment. Fourteen of 16 VSDs with inlet extension showed initial color flow signals along the septal tricuspid leaflet and along the ventricular septum. Of 23 perimembranous VSDs with outlet extension, 19 had flow signals moving directly toward the right ventricular outflow tract. One perimembranous VSD with trabecular extension showed flow signals directed anterolaterally toward the right ventricular free wall. Eleven of 13 muscular VSDs were similarly categorized correctly by color Doppler as inlet, outlet and trabecular. All 5 doubly committed VSDs were correctly diagnosed as an area of discontinuity adjacent to the pulmonary valve in the short-axis view with flow signals directly moving through VSD into right ventricular outflow and pulmonary artery. Angiography correctly detected all VSDs and correctly classified their site and extension in 45 of 58 (77.5%). It misclassified 8 of 40 perimembranous, 3 of 13 muscular and 2 of 5 doubly committed VSDs. Color Doppler compares favorably with angiocardiography in the detection and localization of VSDs. © 1989.