The purpose of this study was to examine possible mechanisms of the obstructive and restrictive ventilatory defects of grain elevator workers. We found that grain handlers whose skin tests were positive to grain or fungal antigens had no excess of respiratory symptoms or pulmonary function abnormalities. Also, those having a possible work-related repiratory problem showed no response to inhalation challenge tests with grain dust extract. In addition, grain handlers exhibited neither an increase in positive serum precipitin tests with fungal antigens nor abnormal serum levels of C3 and C4, C-reactive protein, rheumatoid factor or antinuclear factor. However, their serum a1-antitrypsin level was elevated. The latter finding may be indicative of a pulmonary inflammatory process, but we have found no clear indication of a type 1 or 3 allergic state in grain elevator workers.