In order to study the effect of welding fumes on lung function, 74 high-exposed welders and 31 age-matched electricians were examined in 1982. None had ever smoked tobacco or been exposed to known or potentially noxious agents to the lungs. A significant difference was found between the welders and the control group in vital capacity, total lung capacity, forced expiratory volume in one second, peak expiratory flow rate, maximal expiratory flow rate at 75% of vital capacity, diffusion capacity and slope of the alveolar plateau. The lungs of the welders were physiologically 10-15 years older than those of the control group. Thirty percent of the welders had a well defined respiratory disease. Their lung function impairment was predominantly obstructive (16 persons), but restrictive patterns were also seen (6 persons).