A new generation of transoesophageal echocardiographic probes with a novel matrix array technique has been recently introduced, allowing three-dimensional (3D) presentation of cardiac structures in real-time. This new tool may potentially provide fast and complete 3D information about cardiac structures improving spatial orientation and overcoming limitations of offline 3D technologies. The aim of this study was to demonstrate the feasibility and usefulness of real-time 3D transoesophageal echocardiography (TOE) for the intraoperative evaluation of cardiac surgery procedures. One-hundred patients underwent transoesophageal echocardiographic examination during cardiac surgery as a part of their routine clinical practice. In the intraoperative pre- and post-cardiopulmonary bypass periods complete 2D and 3D transoesophageal examinations were performed. Feasibility and duration of examinations, and immediate additional anatomical value of 3D versus 2D-TOE were annotated intraoperatively. Image quality, additional clinical value of 3D- compared to standard 2D-TOE and the accuracy in the description of mitral valve pathology by a surgeon and an echocardiographer were evaluated off-line. No complications related to transoesophageal examination occurred and successful intubation was achieved in all 100 patients. Therefore, 200 examinations were performed and analysed considering the pre- and post-cardiopulmonary bypass periods. The mean number of acquisitions per patient was 16 +/- 14, including 3D real-time, zoom, full-volume and colour full volume modalities. The duration of the 3D examination was 16 +/- 10 min and the mean image quality score 2.8 +/- 0.7 (in a scale 1-4). In 36 out of 100 cases (36%) 3D-TOE provided additional anatomical information. The surgeon evaluated 3D images easier and more accurately than 2D images (88% vs. 76% in the evaluation of mitral valve scallop). Real-time 3D TOE may be used routinely for the intraoperative evaluation of cardiac surgery. Imaging with this new probe facilitates intraoperative evaluation of several surgical procedures with an additional clinical value in selected cases.