Background: Transesophageal echocardiography allows a semi-invasive hemodynamic monitoring, during cardiac and non cardiac surgery. The benefits of such surveillance must be assessed, since it may help to change patient management. Aim: To assess the usefulness of transesophageal echocardiography during surgical procedures in critical patients. Material and methods: Based on the indications of the North American Societies of Cardiology and Anesthesiology, 264 patients were monitored using a multiplanar transducer. The type of surgery, insertion difficulties, quality of visualization, complications and usefulness of the method were recorded. Results: One hundred eleven cardiac and 153 non cardiac surgical procedures were monitored. In 97% of cases, visualization was good. In 2 cases, it was impossible to obtain a transgastric axis. No complications of the procedure were recorded. The method was useless in nine patients, helpful to change drug and volume management in 126 (48%) patients, helpful to change perioperative management in 49 (19%) patients and was a substitute for pulmonary artery catheterization in 79 (30%) patients. Conclusions: Intraoperative transesophageal echocardiography is a safe technique that renders high quality images, with a low incidence of complications and that, when well indicated, orients therapeutic changes in 98% of patients (Rev Méd Chile 2004: 132: 823-31)