Our objective was to identify risk factors for development of immunologically mediated respiratory disease in workers exposed to hexahydrophthalic anhydride. We performed a medical and immunologic survey study of 57 workers in a workplace molding operation utilizing hexahydrophthalic anhydride. The main outcome measurements were the development of a respiratory disease due to specific IgE antibody (asthma and/or rhinitis) or specific IgG antibody (hypersensitivity pneumonitis or hemorrhagic rhinitis). Of the 57 workers, 7 had both IgE- and IgG-mediated disease, whereas 9 had only IgE-mediated disease. Although neither smoking, age, nor race were risk factors for development of immunologically mediated disease, exposure level and specific antibody were. In conclusion, development of immunologically mediated respiratory disease due to hexahydrophthalic anhydride is most closely associated with exposure level and development of specific IgE or IgG antibodies.