The results are presented for a health control program using 236 male workers exposed to a cobalt inhalation risk. The study group consisted of grinders, producers of diamond tools, workers in metallurgical and mechanical industries (where Widia tools are processed and sharpened), and finally formerly exposed workers. All subjects received a clinical examination, the European Community for Coal and Steel questionnaire on respiratory complaints, a chest X-ray, pulmonary function test, electrocardiogram and determination of urinary cobalt; in 91 subjects, the metacholine bronchial provocation test was performed. Three cases of interstitial lung disease were identified. There were no cases with a significant alteration of ventilatory function while 20 cases (16 exposed and four formerly exposed workers) showed a reduced carbon monoxide transfer coefficient (TL,CO,sb/Va).