In the postinfarct ventricular septal rupture, an early surgical intervention improves prognosis. A rapid and accurate diagnosis is necessary. A 56-year-old patient was admitted to the hospital with a Q-wave posterior myocardial infarction. Auscultation suggested a ventricular septal defect. Neither M-mode nor the two-dimensional echocardiography with apical four- chamber view could confirm the ventricular septal defect. Only the subcostal view showed a basal ventricular septal defect, which was sometimes covered by the septal leaflet of the tricuspid valve. With the continuous wave Doppler, a left-to-right shunt on the ventricular septum could be registered and the pressure in the right ventricle could be measured. Catheterization confirmed the diagnosis of a basal ventricular septal defect with the associated pressure characteristic. The basal ventricular septal defect was successfully closed with a patch. The high accuracy of the continuous-wave Doppler, which is superior to M-mode and two-dimensional echocardiography, was confirmed by this report. Pressure measurement in the right ventricle by continuous wave Doppler also provides a non-invasive diagnostic method that can be used at the bedside.