A total of 132 studies were identified, of which 25 studies addressed environmental exposure to polycyclic aromatic hydrocarbons (PAHs) in the general population. Of these 9 studies included children. Of 101 studies among workers in various occupations, 32 studies were in petrochemical industries, 29 studies in foundries, 14 studies in asphalt work, 21 studies working in urban air, 6 studies in combustion, 3 studies in soil remediation, and 2 studies in printing. Environmental and occupational studies were identified through an extensive search of the PubMed database up to November 2006. The aim of this review was to provide an overview of studies using urinary 1-hydroxypyrene (1-HP) as a biomarker of environmental and occupational exposure to PAHs. Hereby, we aim to support the current validation of 1-HP by summarizing the evidence of specific PAH exposure and1-HP associations in humans. Urine from more than 7000 children from 8 countries and 3400 adults from 9 countries were included in the 25 studies assessing environmental exposure to PAH. Among the occupational studies 7500 men and women gave urine samples to assess occupational PAH exposure. When measuring biomarkers in urine, volume (and time) or concentrations of creatinine are often used to standardize for diuresis. To be able to compare the included studies we recalculated the given concentrations to mumol 1-HP/mol creatinine. In conclusion, the highest concentrations of urinary 1-HP are found among workers in petrochemical industries among coke-oven workers. Occupational PAH exposure was the major factor determining high urinary concentration of 1-HP. The highest concentrations were observed among workers in the petrochemical industry at work places in Taiwan and China. To evaluate environmental and low-level occupational exposure to PAH it is crucial to provide knowledge on intra- and inter-individual variation in the evaluation of 1-HP. The highest contribution originates from environmental tobacco smoke, but also different country, cooking culture, and behavior influences urinary of 1-HP.