Asbestos fibers cause persistent induction of the oxidative stress sensitive transcription factors nuclear factor kappa-B (NF-kappa B) and activator protein-1 (AP-1) in mammalian cells. These transcription factors play an important role in the regulation of cellular activity. Lipid peroxidation, mediated by reactive oxygen species, is thought to be a possible mechanism in the pathogenicity of asbestos fibers. These studies were designed to determine if crocidolite asbestos-induced lipid peroxidation plays a role in the mechanism of formation of NF-kappa B and AP-1. Treatment of a rat lung fibroblast cell line (RFL-6) with crocidolite asbestos in the presence and absence of the membrane antioxidant vitamin E decreased the levels of crocidolite-induced AP-1 and NF-kappa B to background levels. Preincubation of RFL-6 cells with 5,8,11,14-eicosatetraynoic acid, an inhibitor of arachidonic acid metabolism, prior to exposure to crocidolite, abrogated crocidolite-induced NF-kappa B DNA-binding activity to background levels. Coincubation with indomethacin, a cyclooxygenase inhibitor, had no effect on NF-kappa B DNA-binding activity induced by crocidolite. However, nordihydroguaiaretic acid, a lipoxygenase inhibitor, decreased levels of NF-kappa B to background levels. This would suggest that lipoxygenase metabolites of arachidonic acid, produced following lipid peroxidation, are involved in the cellular signalling events to NF-kappa B transcription factor induction by asbestos.