The aim of this study was to assess the diagnostic value of intraoperative 2-D color Doppler transesophageal echocardiography (ITEE) for the surgeon and anesthesiologist in patients undergoing coronary bypass surgery or heart valve replacement. Information given by ITEE in 100 cardiac operations was documented. We judged the ITEE information, considering to what extent it was not to be obtained by other methods and to what extent it influenced the operation itself. The value was classified as dispensable (0), informative (1), valuable (2), or essential (3). In 50 consecutive patients with heart-valve replacement (25 aortic valve prostheses, 25 mitral valve prostheses) ITEE was 38 x (0), 8 x (1), 4 x (2). In 50 consecutive patients undergoing coronary artery bypass graft surgery it was 33 x (0), 11 x (1), 4 x (2), 2 x (3). The two essential diagnoses referred to undetected vein graft occlusions. Information classified as valuable mainly referred to left and right ventricular function or valvular and prosthetic valve function when difficulties occurred during and after extracorporeal circulation. In conclusion, information given by ITEE, although generally regarded as dispensable in the procedures considered, was valuable in 10% of cases and in 2% even essential.