Objective The aims of this study were to analyze the features of mitral valve (MV) prolapse on the real-time 3-dimensional transesophageal echocardiography (RT-3D-TEE) and to explore the value of RT-3D-TEE for localizing the mitral valve prolapse.Methods Twenty-three patients undergoing MV repair or MV replacement for mitral regurgitation (MR) were studied prospectively.Intraoperative RT-3D-TEE examinations wereperformed.The features and locations of MV prolapse on the RT-3D-TEEwere analyzed and compared with the anatomic findings reported by the cardiac surgeons.The surgical view from the left atrium was used when analyzing the RT-3D-TEE features of MV prolapse.Results The surgical view from the left atrium were clearly demonstrated in all of the 23 patients and 138 segments were studied.Preoperative 33 segments of MV prolapse were diagnosed and 105 segments were normal.Of the MV prolapse, the chordal ruptures were found in 16 patients and the vegetations were found in 3 patients.The sensitivity, specificity, positive predictive value, negative predictive value and the overall accuracy of localizing the MV prolapse for the RT-3D-TEE were 91.4%, 99%, 97.0%, 97.1% and 97.1%respectively.Additionally, the overall accuracy of identifying the ruptured chordae tendineae and vegetations was respectively 99.3% and 100%.Conclusions RT-3D-TEE is an effective imaging tool for diagnosing MV prolapse and can provide some additional and helpful information.