The role of monoplane transesophageal echocardiography (TEE) in rapid decision making process was investigated in 115 critically ill patients (pts) with early postoperative complications after cardio-thoracic surgery (hypotension, central venous pressure and/or wedge pressure elevation, electrocardiographic S-T segment elevation). Systolic and diastolic function of left ventricle, left ventricular wall motion abnormalities, right ventricular function, valves or prosthetic valves function, left ventricular outflow tract and morphologic changes were evaluated. Echocardiographic diagnoses were classified as: useful, incomplete, not diagnostic, misleading, unexpected. Echocardiographic diagnoses were confirmed by surgical or pathologic findings in all patients operated or dead. All but one patients, who needed surgical therapy, were operated on the basis of echo-diagnosis alone. Therapeutic changes induced by echo-diagnosis were evaluated and classified as major and minor. Diagnosis was fast (7 +/- 2 m) and sure (no complication). TEE was useful in 91% of cases (105/115 pts), incomplete in 2.3% (3/115 pts), not diagnostic in 2.3% (3/115 pts) and misleading in 3.4% of cases (4/115 pts). TEE findings made major therapeutic changes necessary in 66.9% (77/115 pts); there was a shift from medical to surgical therapy in 28% (41/115 pts); in 14.7% (17/115 pts) minor changes in drug therapy were made. TEE was also useful in quick and safe placement of devices (Swan-Ganz catheter, intra aortic balloon pump, endocardial pace maker, ventricular assist device) and in guiding urgent pericardiocentesis. The effects of medical therapy and evolution of ventricular dysfunction were well monitored by TEE. In our experience TEE was a very useful tool for management of early complications after cardio-thoracic surgery.