The metabolism of toluene was found to be inhibited by a large dose of alcohol in seven volunteers exposed to 80 ppm of toluene under experimental conditions. When alcohol was taken during exposure, blood toluene concentrations were 42.5% greater on average than during exposure with no alcohol. This is probably due to competition for alcohol dehydrogenase which is required for the breakdown of both ethanol and toluene. In men exposed to toluene at work, it was found that blood toluene concentrations were lowest in those who drank regularly. These results suggest that continued alcohol intake increases the metabolism of toluene, presumably by inducing the microsomal oxidising enzyme system in the liver.