Urinary PAH-metabolite excretion by non-exposed volunteers, temporarily living on a PAH-poor and PAH-rich diet, respectively, as well as by occupationally PAH-exposed coke plant workers and road workers has been studied. Significant differences in the amount of the metabolites excreted in the urine were detected; the ratio of various metabolites was also found to be different. The mass excretion per liter of the metabolites from phenanthrene was found to be for the unexposed volunteers about 3.5 μg/1, for coke plant workers about 70/μg/l and for road workers about 35 μg/1. For the metabolites of chrysene the values were 0.03 μg/1 2.5 μg/1 and 0.09μg/1, respectively, and for the total metabolites of benzo(a)pyrene: 0.006 μg/l for unexposed persons, 0.37 μg/1 for coke plant workers and 0.019 μg/1 for road workers. © 1991, Taylor & Francis Group, LLC. All rights reserved.