We identified 12 new cases of hypertrophic cardiomyopathy (HCM) and 3 new cases of dilated cardiomyopathy (DCM with echocardiography) in 72980 (aged 18-85 years, 43.1 +/- 14.1) industrial workers during an annual health check from April to October in 1996. Two of 3 patients with DCM were males, 21 and 25 years of age. No patients had symptoms. ST-T abnormalities by electrocardiography were found in 87% (13/15) of patients with cardiomyopathy and left ventricular hypertrophy (LVH) in 53% (8/15). Our findings suggest that echocardiography is important in mass screening for early detection of asymptomatic cardiomyopathy in middle-aged as well as young patients with ST-T abnormalities.