In this study, the authors evaluated exposure to airborne polycyclic aromatic hydrocarbons (PAHs) in workers exposed to exhaust gas from cars, and they assessed the efficiency of urinary 1-hydroxypyrene as an indicator of exposure to pyrene and PAHs. The authors selected 2 groups of police who worked in 2 areas in the city of Florence: 1 group was highly exposed to high-density traffic emissions during the winter and summer of 1997, and the 2nd group experienced low exposure to traffic emissions during the same period. Ambient monitoring was achieved with personal sampling of airborne PAHs during each workshift. Eight hydrocarbons were used as indicators of pollution caused by PAHs (e.g., pyrene, benzo[a]pyrene, benzo[a]anthracene, dibenzo[a,h]anthracene). Biological monitoring was performed through dosing of 1-hydroxypyrene (pyrene metabolite) in urine samples taken at the end of each workshift. The ambient monitoring revealed that PAH concentrations were influenced by both season of sampling and varying intensities of traffic in the different areas. The median concentration of benzo[a]pyrene in winter was twice as high in the high-density traffic area as in the low-density traffic area (i.e., 4.1 ng/m3 versus 1.8 ng/m3). In summer, the high-density traffic area experienced benzo[a]pyrene concentrations that were 6 times higher than in the low-density traffic area (i.e., 1.2 ng/m3 versus 0.2 ng/m3). Benzo[a]pyrene was also correlated highly (r(s) = .92, p < .0001) with the mixture of total PAHs analyzed, thus confirming its function as a good indicator of exposure to PAHs in an urban environment. Levels of urinary 1-hydroxypyrene appeared to be generally influenced by the intensity of traffic, especially during the winter (i.e., median value in winter was 199.2 ng/gm creatinine in the high-density traffic area and 120.5 ng/gm creatinine in the low-density traffic area). An analysis of the general data revealed that 1-hydroxypyrene was, to some degree, related to pyrene, benzo[a]pyrene, and airborne total PAHs, whereas analysis of separate data for the area and the season revealed an emergence of a closer correlation during the winter in the high-traffic area. Therefore, 1 -hydroxypyrene can be considered a good biological indicator of exposure to airborne PAHs in the urban environment, especially in winter and in high-density traffic areas.