Background : Duchenne-type muscular dystrophy(DMD) is the most common hereditary neuromuscular disease which account for 80-85% of the total cases with dystrinopathy. It is clinically characterized by proximal weakness and wasting, leading to immobility in the early teens. The onset is in early childhood and the most patients die of respiratory failure(75%), heart failure(20%), pneumonia, pulmonary embolism or sudden death. As successful management of the skeletal and respiratory aspects such as overnight assisted ventilation has resulted in increasing the mobility and the life expectancy, cardiac pathology has become an increasingly important determinant of their functional capacity and survival. The cardiomyopathy is usually latent initially without symptoms or over clinical signs. Patients with DMD often have dyspnea. Respiratory muscle weakness, scoliosis, cardiac involvement is thought to be the cause of dyspnea. We investigated the incidence and risk factor of cardiac involvement in adolescent and adult patients with DMD. Method : From January 2004 to June 2005, we enrolled 20 male patients with DMD (aged 20.6짹3.0 years-old) who were admitted due to dyspnea at the Yongdong Severance Hospital. The neurologic diagnosis was made either by genetic study or muscular biopsy. Serum B-type natriuretic peptide level and creatine-kinase level were checked. 12-lead electrocardiogram and transthoracic echocardiography was performed to evaluate the cardiac function. Left ventricular ejection fraction(LVEF) was measured by M-mode. Result : All patients were on sinus rhythm during the exam. Ten patients had sinus tachycardia(50%). Other electrocardiographic abnormalities were first-degree AV block(1 pt), LAD(1 pt), and RBBB(6 pts). Patients with reduced LVEF(<50%) were older compared with normal or preserved LVEF(= or >50%)(22.1 vs 19.3 years-old, p=0.037). There was tendency of increased s-BNP(114.1 vs 52.1 pg/mL) and longer duration of DMD(14.1짹3.6 vs 11.9짹3.6 years) in patients with reduced LVEF. Conclusion : Cardiac involvement in adolescent and adult patients with DMD is important and frequent. Therefore more active cardiac investigation is thought to be required in patients with DMD as they get older.