Diesel exhaust is considered a probable human carcinogen by the IARC. Biomonitoring of workers occupationally exposed to diesel exhaust was performed to determine their internal burden of diesel associated aromatic compounds. Personal air sampling also allowed to determine the exposure of the miners at their work place towards several polycyclic aromatic hydrocarbons (PAH) and nitro-arenes, the latter of which are thought to be specific constituents of diesel exhaust. For biomonitoring the urine of 18 underground salt miners was collected during and after their shift for 24-hours. half of the 18 miners were smokers. The urinary levels of 1-hydroxypyrene and hydroxylated phenanthrene metabolites were determined as biomarkers of PAH exposure, whereas urinary levels of some aromatic amines were chosen to monitor exposure towards specific nitro-arenes from diesel exhaust like 1-nitropyrene and 3-nitrobenzanthrone and to monitor the human burden by these compounds from inhaled cigarette smoke. Non-smoking workers exposed to diesel exhaust excrete an average level of about 4 micrograms phenanthrene metabolites, whereas the urinary levels in smokers were up to 3-fold higher. In summary the results indicate that (i) diesel exposure led to an increase of PAH metabolism in the workers examined, most probably by an induction of cytochrome P450 (ii) smokers could be identified in accordance with earlier studies by their increased ratio of phenanthrene metabolites derived from 1,2- and 3,4-oxidation and their higher amounts of excreted 1-naphthylamine, and (iii) the excreted amounts of aromatic amines found as metabolites of the nitro-arenes were about 5- to 10-fold higher as one might expect from the levels determined by personal air sampling at the workplace of the individuals.