In a 3-year survey, respiratory symptoms, spirometry, and methacholine reactivity were measured annually in welders (n= 51) and non-welder control subjects (n= 54) to determine whether welding-related symptoms are associated with accelerated decline in lung function or changes in airway reactivity. In the across-workshift study, maximal midexpiratory flow rate declined reversibly during a welding day, whereas 1-second forced expiratory volume and forced vital capacity were unchanged. In the longitudinal study, the welders had significantly more reversible work-related symptoms of cough, phlegm, wheeze, and chest tightness than the non-welder shipyard control subjects. In this group of actively working welders, across-workshift changes in midflow and reversible symptoms were related to the welding occupation, but evidence for chronic irreversible effects on spirometry or airway reactivity was not seen over the 3 years of observation. The short period of observation was not optimal for detecting a chronic effect on lung function. Work practices and engineering controls may be successfully preventing irreversible respiratory effects, but not mild reversible effects, in this group of welders.