We describe immunologic responses in subjects exposed to glutaraldehyde (GA) who were diagnosed as having occupational asthma, or who described work-related respiratory symptoms. A series of GA-modified proteins was characterized, and used to analyse sera from 20 GA-exposed workers and 21 unexposed workers for IgE antibodies. Inhibition studies were used to determine the specificity of binding. The reaction of GA with albumin in different molar ratios produced a range of modified proteins, which were used to measure specific IgE antibodies. A significant difference between exposed and unexposed subjects with serum IgE less than 150 kU/l could be detected for GA-specific IgE antibodies (P - 0.026), and 31% of exposed workers with occupational asthma had antibody levels greater than the unexposed population (mean +2.5 SD). False-positive results were obtained with serum from unexposed workers who had total IgE levels greater than 150 kU/l, but this binding was not inhibited by GA-modified proteins. We report the first evidence of immunologic sensitization in some workers exposed to GA. However, GA may behave like many other low-molecular-weight chemicals in that specific antibodies can be detected in only a small percentage of exposed workers who report work-related respiratory symptoms.