The relationship of skin reactivity and IgE serum level to the prevalence of chronic respiratory symptoms and ventilatory capacity in workers exposed to different organic aerosols and in control workers is presented. In general, the exposed workers had a higher prevalence of positive skin tests to occupational allergens than the controls, with the exception of soy-bean workers. The workers with positive skin tests to occupational allergens had a higher prevalence of almost all chronic respiratory symptoms although the differences did not always reach statistical significance. Among workers with positive skin reactions the prevalence of increased IgE serum level was significantly higher than among those with negative skin reactions. There were large mean relative acute across-shift reductions of ventilatory capacity in all groups of exposed workers, varying for FVC from 1.7 to 13.3%, for FEV1 from 0.4 to 21.9%, for FEF50 from 1.5 to 16.1% and for FEF25 from 0 to 24.9%. However, there was no correlation of acute and chronic lung function changes with skin reactivity or IgE serum level. Our data suggest that although exposure to organic aerosols may cause immunological reactions, it appears that such changes are not caused by allergic mechanisms. On the basis of positive skin reactivity or IgE serum level the workers who are prone to the development of chronic respiratory impairment cannot be predicted with certainty.