Immune responses and pulmonary function were assessed as part of a NIOSH Health Hazards Evaluation in 36 workers involved in the production of industrial enzymes from bacteria and fungi following complaints of asthma and flu like symptoms. Environmental exposure was assessed by measuring the activities of alkaline-protease and amyloglucosidase and total protein in air samples. Workers were examined using epicutaneous threshold titration testing, enzyme linked immunosorbent assay of blood samples, and pulmonary function tests. Exposed workers had significant increases in the prevalence of respiratory, ocular, nasal irritation, and flu like symptoms as well as in sweating and muscle aches. Forty two percent of the subjects reported having two or more symptoms associated with allergies and 25% had two or more symptoms associated with a flu like illness. Significant increases were seen in the percentage of workers with positive skin reactions to selected antigens, 50% had positive skin reactions to commercial alkaline-protease, 22% reacted to commercial amyloglucosidase from Aspergillus-niger (AGAn), and 22% reacted to amyloglucosidase from noncommercial A-niger (CAGAn). The number of workers identified as atopic was significantly increased as well. Significant increases in mean IgG specific antibody levels for alpha amylases from B-licheniformis, B-subtilis formulation 1, B-subtilis formulation 2, commercial A-oryzae (CaAAo), AGAn, and CAGAn and in mean serum IgE specific antibodies for CaAAo and AGAn were seen among exposed workers compared with referents. An increased risk for mild obstructive or restrictive results on lung function testing was seen among process operators and a significant number of workers tested positive for asthma using peak flow determination. The authors conclude that occupational exposure to industrial enzymes may induce cutaneous hypersensitivity, increase antibody levels, and alter lung function.