Transesophageal echocardiography (TEE) is a new monitoring technique that images the heart and provides information on regional wall motion and left ventricular filling. However, despite its potential for inaccuracy due to its retrocardiac position and angulation, TEE has not been validated by another imaging technique. Using direct on-heart echocardiography (OHE) as a standard, the authors evaluated the ability of TEE to measure accurately left ventricular end-diastolic area (EDa), end-systolic area (ESa), and ejection fraction area (EFa). Ten patients with coronary artery disease without evidence of valvular dysfunction undergoing myocardial revascularization were studied. A Diasonics® 3.5 MHz two-dimensional TEE probe was introduced into each patient's esophagus and positioned to obtain a view equivalent to the parasternal short-axis projection. A similar view was obtained by OHE using a sterilely prepared 3 MHz ATL® probe placed on either the pericardium or epicardium. In each patient, immediately prior to and after pericardiotomy, both transesophageal and on-heart short-axis views at the level of the papillary muscles were obtained. Using a dedicated Diasonics® computer echoanalyzer, EDaand ESafrom four consecutive cardiac cycles were outlined with a light pen and averaged. EFawas calculated by the formula EFa– (EDa– ESa)/EDa. Seventeen comparable transesophageal and on-heart echocardiograms were obtained. ESaby TEE correlated well with ESaby OHE (15.13 ± 9.62 cm2vs.14.92 ± 10.53 cm2; r = 0.94). Similar results were obtained for EDa(27.75 ± 9.88 cm2vs.30.40 ± 13.99 cm2; r = 0.88) and EFa(0.49 ± 0.17vs.0.54 ± 0.13; r = 0.92). TEE can accurately assess left ventricular filling and ejection.