Objective: To assess the value of transesophageal echocardiography (TEE) during cardiac surgery. Method: Intraoperative TEE was performed to record left atrial gas during and for 15 minutes after bypass in 131 pa tients and to evaluate mitral regurgitation after mitral replacement in 38 patients. The degrees of the gas and mitral re gurgitation by TEE was visually quantified on a 4-point scale(0 to 3) and a 5-point scale(0 to 4), respectively. Result: The left atrial gas was detected in 115(88%)patients, two of which with positive echograms(gas grade=3). There was significant improvement in the mean mitral regurgitation grade after mitral replacement (3.4?0.6 to 0.5?0.2, P