Acute exposure of rats to acrolein (1 or 2 ppm) resulted in reduced levels of glutathione, ascorbic acid and alpha-tocopherol. The activities of catalase and glutathione peroxidase were reduced whereas an increase in the activities of superoxide dismutase was observed. This led to enhanced lipid peroxidation, which produced extensive lung damage as indicated by the elevated levels of the biochemical markers--angiotensin converting enzyme, lactate dehydrogenase, protein and lactate in the bronchoalveolar lavage.