A male subject exposed for many years to metal dusts from grinding and cutting hard metals was investigated four years after the exposure ceased. While chest x-ray films and histologic examinations showed diffuse interstitial fibrosis and severe perivascular and peribronchiolar fibrosis, radiochemical neutron activation analysis (NAA) showed high W, Ta and Co concentrations in the pulmonary specimen compared to the corresponding determinations in 17 control subjects. Tantalum was also found in high concentrations in bronchoalveolar lavage fluid (BAL) and in the blood. In addition other elements such as Ni, Cr, Th and Cd were found in the lung biopsy specimen of the worker in amounts significantly higher than in the control subjects. The results suggest that hard metal origin of pulmonary fibrosis can be detected many years after removal from exposure.