The use of ultrasonic imaging in patients undergoing cardiac surgery continues to grow. Recent data have substantiated the utility of intraoperative transesophageal echocardiography in the patient with mitral valve disease. This technique has become the procedure of choice for the on-line assessment of the degree of mitral regurgitation before and after cardiopulmonary bypass. Transesophageal echocardiography is being more widely used for the detection of regional wall motion abnormalities intraoperatively because recent data suggest that hemodynamic parameters may be insensitive for the detection of ischemic events. In the evaluation of patients with congenital heart disease and suspected aortic dissection, transesophageal echocardiography is becoming increasingly important. Newer applications of ultrasonic techniques include contrast echocardiography for evaluating myocardial perfusion and intraoperative evaluation of the ascending aorta for detecting atherosclerosis, which may be a source of atheroembolism. Ultrasonic imaging has become invaluable in the treatment of patients undergoing cardiac surgery.