Transthoracic Doppler echocardiography has been shown to be a sensitive modality for the diagnosis of acute septal ruptures after myocardial infarctions. Transesophageal echocardiography has been shown to improve diagnostic accuracy and image quality in many clinical settings. We performed transesophageal Doppler echocardiography in 10 patients with acute septal ruptures. Transesophageal echocardiography provided improved visualization of the rupture morphology (6 of 10 by transthoracic versus 10 of 10 by transesophageal imaging), better detection of multiple rupture sites (2 by transthoracic, 5 by transesophageal study) and better detail of the direction of shunt flow. On the basis of the transesophageal echocardiographic appearance, we propose that septal ruptures after acute myocardial infarctions be classified as simple or complex, consistent with pathologic criteria for left ventricular septal and free wall ruptures. Transesophageal echocardiography proved a useful and safe adjunct to transthoracic imaging, overcoming the technical limitations in these critically ill patients.