Abstract: Background: Cardiac involvement is not a common feature of Behcet's disease (BD), but may be a sign for poor prognosis. There are only few case reports in the literature and the prevalence of cardiac involvement in BD is not exactly known. Our study was designed to find the prevalence and characteristics of cardiac involvement in Iranian patients with BD. Methods: All new cases referred to Behcet's clinic for diagnosis in a 6-month period, were enrolled in a double blind case control study. The cardiologist was unaware of the diagnosis. A complete clinical examination, electrocardiography (ECG), chest X-rays (CXR) and echocardiography (M-mode, two dimensional, doppler, color flow mapping) was performed for all. Patients diagnosed as BD were compared to those not having the disease (control group) by chi square test. 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 of different manifestations in BD and control groups were as follow: Cardiac symptoms 30%±9 vs 39%±8 (p:0.12), cardiac signs 12.5%±6 vs 16%±6 (p:0.42), abnormal ECG 3%±3 vs 5%±4 (p:0.26), abnormal CXR 2%±3 vs 3.5%±2 (p:0.26), and abnormal echocardiography 29%±9 vs 23%±7 (p:0.27). The most common cardiac abnormality was mitral valve prolapse (MVP), seen in 27% (CI:8.5) of BD and in 17% (CI:6.2) of the controls, with no statistically significant difference (p:0.08). MVP was not related to sex, pathergy phenomenon, HLAB5 and HLAB27 positivity (p>0.05). Findings such as left ventricular dysfunction, arrhythmia and interatrial septal aneurysm was encountered uncommonly. 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.