The induction of cardiac effects in hard metal workers is uncertain. This study investigates cardiac function of a group of 31 hard metal workers with or without pulmonary disease. The average duration of exposure to cobalt containing dusts was 10.4 years (range 1-30), while the environmental levels of cobalt exposure ranged from 0.09 to 13.6 mg/m3 Co. Cardiac function has been studied by: ECG (electrocardiogram), exercise test (ET), ECG 24 h according to Holter (ECGH), echocardiogram (ECHO) and radionuclide angiocardiography with 99Tc (RNA). The aims of this work were (i) to show the existence of cobalt myocardiopathy in the workers analyzed and, (ii) to find an early indicator of cardiac dysfunction which could be used in the clinical examination of hard metal workers. Within the group of patients with hard metal lung disease, cases of myocardiopathy of doubtful aetiology have been found. The cardiac indexes obtained through RNA show ventricular dysfunction in healthy hard metal workers which could be a manifestation of initial pulmonary artery hypertension or of an early occult cor pulmonale due to an unknown fibrotic lung disease.