OBJECTIVES: This study explored the possibility of using urinary 1-naphthol excretion as a marker of complex exposure among workers handling creosote METHODS: Urine specimens of 6 workers from a creosote impregnation plant, where railroad ties were impregnated with coal tar creosote, were collected during 1 workweek, and the concentration of 1-naphthol was determined. 1-Naphthol in spot urine samples of 5 occupationally nonexposed male smokers was used as the background reference. Concurrently, naphthalene and 10 different polycyclic aromatic hydrocarbons (PAH) were determined in personal air samples. RESULTS: The mean airborne exposure of the workers was 1.5 mg/m for vaporous naphthalene, 5.9 µg/m for particulate PAH and 1.4 µg/m for PAH with 4-6 aromatic rings. The mean urinary concentration of 1-naphthol at the end of the workshift was 20.5 (range 3.5-62.1) µmol/l, whereas the referents` urinary concentration was below the detection limit (0.07 µmol/l). Airborne naphthalene correlated fairly well with 1-naphthol when measured at the end of the shift (r=0.745). CONCLUSION: This method of analysis for 1-naphthol is sufficiently sensitive for measuring low occupational exposures to naphthalene. Low background exposures are, however, unlikely to result in detectable urinary levels of 1-naphthol. Since naphthalene is the most abundant compound in creosote vapor, urinary 1-naphthol determination serves well as a biological marker of exposure to vaporous creosote. Urinary 1-naphthol alone is not, however, a suitable marker for inhalatory or cutaneous exposure to PAH originating from creosote.