A group of 288 workers of a graphite electrode manufacturing plant (33 of whom were not classified as either exposed or non-exposed) participated in a biological monitoring programme of exposure to PAHs via determination of 1-hydroxypyrene in end-of-shift urine. A highly significant difference (p < 0.000001) was observed in the mean urinary values of the metabolite in the 132 subjects classified as exposed compared to the 123 not exposed, which was not influenced by by confounding factors. The maintenance workers group showed mean urinary levels of 1-hydroxypyrene similar to the production department workers who were exposed to pitch. Among the exposed the use of a mask with filters for organic fumes reduced absorption of PAHs and significantly reduced urinary excretion of 1-hydroxypyrene (p < 0.005). The test also proved to be sensitive in discriminating the subjects exposed to low doses of PAHs, as the results obtained in laboratory workers showed. After comparing their data with the proposals for Biological Limit Values for 1-hydroxypyrene, the authors stress the usefulness of this biological monitoring tool in exposure to PAHs for the assessment of cancer risk, as provided for by Law No. 626/94.