Styrene is known to be hepatotoxic and pneumotoxic in rodents, and these adverse effects are related to its metabolism. Mice deficient in the enzymes responsible for both the activation and detoxification of styrene are useful in examining this relationship more closely. In the current study, mice deficient in glutathione S-transferase P1P2(-/-) (GST(-/-)) were compared with wild-type mice. Similar changes in serum sorbitol dehydrogenase, as an indicator of hepatotoxicity, and bronchioalveolar levels of protein, cells, and lactate dehydrogenase, as indicators of pneumotoxicity, were observed after styrene administration. Glutathione depletion followed a similar pattern. The administration of the toxic metabolite, styrene oxide, which is a direct substrate for glutathione metabolism, and 4-vinylphenol, which is a minor metabolite but is more potent than either styrene oxide, yielded results similar to those of styrene. The results indicate that either other isoforms of glutathione S-transferase are more important than the P1P2 form in styrene detoxification or that this pathway contributes in only a minor way to styrene detoxification, compared to other pathways.