Twenty-three of 34 workers who had worked in the injection molding operation making polyurethane foam parts at an automobile parts manufacturing plant developed respiratory symptoms and/or systemic symptoms over a 2-month period following the full production use of a new diisocyanate paint that contained 1,3-bis(isocyanatomethyl)cyclohexane pre-polymer (BIC)(CAS #75138-76-0, 38661-72-2). At 3 months, all subjects underwent an interview, physical examination, pre- and post-shift pulmonary function tests, and either methacholine challenge test or bronchodilator challenge at an occupational health clinic. The most frequently cited symptoms were dyspnea (65%), cough (61%), chest tightness (57%), chills (57%), wheezing (30%), and myalgias, arthralgias, and nausea (26%). Thirteen subjects had either a positive methacholine challenge test or a positive response to bronchodilator challenge, making the overall prevalence of airway hyperresponsiveness 38%. The overall prevalence of hypersensitivity pneumonitis-like reactions among line operators in the injection molding process was 27%. This disease outbreak suggests that 1,3-bis(isocyanatomethyl)cyclohexane pre-polymer may cause asthma and hypersensitivity pneumonitis-like reactions. The use of BIC was discontinued 6 months after the first workers developed symptoms.