['The Eustachian valve (EV) is an embryonic structure redirecting the blood flow from the inferior vena cava through the foramen ovale. It may persist in adults as a floating membrane in the right atrium. A large EV can be associated with thrombosis, embolization, bacterial endocarditis, etc. The prevalence of EV in the normal population is unknown.', 'to assess the prevalence and size of EV in unselected patients examined by transoesophageal echo. Methods. 1100 consecutive patients were examined for various reasons by a single operator and interpreter. Routine check was made for the presence of EV in the right atrium. Only patients with a mobile EV and not with a simple rigid rim were counted. Three measurements of the EV length at the level of the aortic valve (i.e. 90°C) were made off-line and the longest distance considered. If the EV was not visualized and recorded as a straight line because of its chaotic movement, the picture of the valve was segmented into several separated valve portions and the sum taken as the true length.', '46 patients (24 males) with EV were identified out of total 1100 pts examined. The average length of the EV was 23.6 ± 9.7 mm (7-47 mm, median 23 mm).'] Do the prevalence of eustachian valve on transoesophageal echo examination?