Abstract: Introduction: Behcet's disease (BD) is a multisystem disease characterized by recurrent oral and genital ulcers, skin and ocular lesions. Other organ involvement occurs as minor manifestations of the disease. Cardiac involvement is not a common feature of the disease, but may be a sign for poor prognosis. The exact prevalence of cardiac involvement is not exactly known, only selected cases are reported in the literature. Our study .was designed to find the prevalence and characteristics of cardiac involvement in Iranian patients with BD. Materials & Methods: All cases referred to Behcet's clinic for diagnosis (comprising BD and non- BD patients), from November 1996 to March I997, were enrolled in a double blind case control study. The cardiologist was unaware of the diagnosis. A complete cardiac examination; clinical, electrocardiography (ECG), chest X-rays (CXR) and echocardiography (M-mode, Two dirnensional, Doppler, Color flow mapping) was jperformed for all. The evaluated cardiac symptoms were chest pain; dyspnea, orthopnea and palpitation. The cardiac signs included: Blood pressure, jugular venous pressure, cyanosis,, edemat cardiac murmurs or abnormal sounds (S3, S4, opening snaps or clicks). Patients diagnosed as BD (according to the Iran and the Japan criteria) were compared to those not having the disease (control group). Chi square test and Fisher exact test were used for statistical analysis. A confidence interval at 95% (CI) was calculated for each item. Results: We evaluated 246 patients (104 BD patients and 142 controls). They were age and sex matched, and there was no significant difference in their cardiac risk factors. The prevalence in BD patients and control group for the following manifestations were as follow: Cardiac symptoms 30%±9 vs. 39%±8, p=0.12. Cardiac si.gns 12.5%±6 vs. 16%±6, p=0.42. Abnormality of ECG 3%±3 vs. 5%±4, p=0.26. Abnormality of CXR 2%±3 vs. 3.5%±2, p=0.26, and abnormality of echocardiography 29%±9 vs. 23%±7, p=0.27. The difference was not statistically significant in any of them. The most common cardiac abnormality was mitral valve prolapse (MVP), seen, in 27% (CI=8.5 of BD patients and in 17% (CI=6.2) of the control group, with no statistically significant difference (p=0.08). MVP was not related to sex, pathergy phenomenon, HLAB5 and HLAB27 positivity (p>0.05). Other cardiac abnormality including left ventricular dysfunction, arrhythmia and interatrial septal aneurysm was encountered uncommonly. Pericardial involvement was not seen. Conclusion: Cardiac involvement was not frequent in newly diagnosed BD patients. Cardiac investigations such as ECG, CXR or Echocardiography are not recommended routinely at the time of diagnosis.