We investigated basic abnormalities of coagulation and fibrinolysis in Duchenne muscular dystrophy (DMD) patients with cardiac dysfunction. Forty seven patients with DMD, aged 13-37 years old, were enrolled. Based on left ventricular ejection fraction (LVEF) results determined by echocardiography, patients were divided into 3 groups: LVEF less than 30% (markedly depressed group), LVEF between 30 and 50% (slightly depressed), and LVEF greater than 50% (normal). We measured serum levels of total fibrin and fibrinogen degradation products (FDP), as well as plasma fibrinogen, thrombin-antithrombin complex (TAT), prothrombin fragment (F1+2), and D-dimer. The levels of TAT and F1+2 in the markedly depressed group were significantly elevated compared with the other groups, whereas FDP, fibrinogen, and D-dimer levels did not differ among the groups. We concluded that activated coagulation is associated with cardiac dysfunction in patients with DMD.