The incidence and nature of cardiac involvement in Behcet's disease are not yet clearly documented. We first used transesophageal echocardiography in combination with resting and signal averaged electrocardiography to define cardiac involvement in Behcets patients. Transthoracic and multiplane transesophageal echocardiography, and resting and signal averaged electrocardiography were performed in 35 Beh et's disease patients (9 women and 26 men, mean age: 38 12 years) and 30 normal subjects. Higher incidences of interatrial septum aneurysm (31% to 6%), mitral valve prolapse (25% to 3%), mitral regurgitation (40% to 6%) and aneurysmal dilatations of sinus valsalva and ascendan aorta were observed in the Beliget's disease patients than in the normal subjects. Mean QT dispersion and mean corrected QT dispersion values were significantly greater in the patients with Beliget's disease. Patients with interatrial septum aneurysm (and/or PFO), valvular dysfunction or proximal aorta dilatation had greater QT dispersion values than thase without these pathologies in the Behqet's group (63+/-11 vs 44+/-19 ms, 58+/-23 vs 41+/-24 and 60 27 vs 42 23 ms respectively, P<0.05). Positive signal averaged electrocardiography parameters were detected in 18 (51%) Beh et's disease patients compared with one (3%) in controls (P<0.001). Dilatation of the proximal aorta, interatrial septal aneurysm, mitral valve prolapse, and mitral regurgitation are the common findings of cardiac involvement in Beliget's disease. Increased dispersion of ventricular repolarisation and positive late potentials are also detected. QT dispersion is significantly higher in patients with these cardiac abnormalities. These findings suggest that cardiac involvement in this disorder is a diffuse process which involves both cardiac structure and vascular elements.