A person exposed to trimellitic anhydride (TMA) an epoxy resin widely used in industry, experienced respiratory failure, anemia, and gastrointestinal bleeding. A lung biopsy specimen demonstrated intra-alveolar hemorrhage and damage to alveolar lining cells. The patient and six co-workers were examined. Results indicated the presence of hemolytic antibodies directed against TMA-haptenized erythrocytes, IgG, IgA, and IgM antibodies directed against TMA-erythrocyte complexes, and antibodies against TMA-human serum albumin. Antibody levels in the patient were greater than in the co-workers. The elevated antibody levels demonstrate the antigenic potential of TMA. However, the cause of the pulmonary and hematologic damage remains uncertain and may represent either immunologic or direct toxic effects of TMA. In patients with multisystem failure of this nature, occupational hazards should be added to the differential diagnosis.