Eighty-eight percent of all 40-year-old male residents of four suburban municipalities of Copenhagen County were examined for the lead concentration in their blood and interviewed regarding job category and place of work. Of the 504 men, 482 were currently employed, 18 were unemployed, and 4 were pensioners. The total median blood lead level was 13 micrograms/100 ml (0.6 µmol/l). Men employed in construction, industrial production, and transportation had the highest lead levels, while very low concentrations were found among pensioners and farmers. Blue-collar works had higher blood lead results than white-collar workers. Very high levels were found in two men employed at a secondary lead smelter, but otherwise increases in lead concentrations were comparatively small. However, the occupationally related, increased blood lead levels identified in this population contributed significantly to normal "background" levels.