Ten consecutive patients with ventricular septal rupture complicating acute myocardial infarction were studied by means of Doppler echocardiography (including two-dimensional, conventional and color Doppler techniques) and bedside right heart catheterization using a Swan-Ganz catheter. One patient died before an operation could be performed. Seven critically ill patients underwent emergency cardiac surgery without preoperative cardiac catheterization, while in two patients it was also possible to undertake coronary angiography before surgery. Two-dimensional echocardiography diagnosed post-infarction ventricular septal rupture in 6 out of 10 patients. Color Doppler revealed the presence and the location of septal rupture in all 10 patients. The color Doppler diagnosis was confirmed either by surgery or necropsy. The estimates of pulmonary artery pressure, obtained by color Doppler-guided continuous wave Doppler beam, were very close to those measured by simultaneous right heart catheterization. In 3 patients, patch leakage occurred 3 days, 15 days and 1 year after the operation. Two-dimensional echocardiography revealed the patch leakage in only one of 3 patients while its location was visualized by color Doppler in all 3 patients. In one patient the color Doppler diagnosis was confirmed at necropsy. In the remaining 2 patients, a small left-to-right shunt was demonstrated by radionuclide studies. Color Doppler echocardiography is a highly sensitive and rapid technique in the diagnosis of postinfarction ventricular septal rupture. In critically ill patients it offers relevant information and may obviate the need for any invasive preoperate investigation.