Summary A group of Fischer F344 rats were exposed to an aerosol of crocidolite asbestos for 36 d. Short-term organ cultures were established from the lungs of these animals and from a similar control group. The ability of these cultures to metabolise benzo(a)pyrene to water-soluble and ether-soluble forms was measured. Crocidolite treatment reduced the lungs ability to produce both types of metabolite although only the reduction in water-soluble forms was significant. DNA binding increased in cultures from treated rats, though this was not statistically significant. The possible relationship of these results to asbestos pathogenesis is discussed.