OBJECTIVES--To study myocardial echo amplitude in Duchenne muscular dystrophy and to examine the implications of increased echo amplitude. DESIGN--Regional echo amplitude, wall motion, and uptake of thallium-201 were examined in the left ventricular wall and the relation between these variables was investigated. SETTING--Hara National Sanatorium, Japan. PATIENTS--Seven healthy controls aged 10-28 years and 14 patients with Duchenne muscular dystrophy aged 12 to 30 years. INTERVENTIONS--Echocardiography with a sector scanner (Hitachi EUB-150, Japan) and a 3.5 MHz transducer (Hitachi EUP-S21, Japan); thallium-201 myocardial single photon emission computed tomography at rest with a rotating gamma camera system (Hitachi RC-135DT, Japan). MAIN OUTCOME MEASURES--Echo amplitude of the myocardium, thickness and wall motion of the posterior wall and ventricular septum, and myocardial uptake of thallium-201. RESULTS--Areas of increased echo amplitude were detected along the outer half of or throughout the posterior wall of left ventricle in nine of the 14 patients. Their posterior walls showed significantly decreased maximal systolic and diastolic endocardial velocities (mean (SE) 31.4 (16.0) and 55.6 (53.5) mm/s) compared with normal subjects (57.7(19.4) and 113.0 (27.5) mm/s), and decreased uptake of thallium-201. Their ventricular septa, however, showed normal echo amplitude and wall motion and normal uptake of thallium-201. CONCLUSION--Areas of increased echo amplitude were detected in the posterior walls of left ventricles of patients with Duchenne muscular dystrophy. These areas were suspected to be the sites of myocardial fibrosis.