This study examines changes in the urinary 1-hydroxypyrene (1-OHP) concentration as a polycyclic aromatic hydrocarbon (PAH) metabolite related to smoking among eight volunteers. The study subjects consisted of 8 participants (2 smokers, 4 ex-smokers and 2 non-smokers; mean age 23, range 21 ~ 24 years old) in a smoking cessation program. Three urine samples were collected each week for 4 weeks from each participant to give a total of 96 urine samples. None of the participants smoked during the study period. Levels of urinary 1-OHP, as an internal dose marker of smoke containing PAHs, were measured by high performance liquid chromatography (HPLC) fluorescence detector. Urinary 1-OHP levels in the ex-smokers were decreased during the 4 weeks study period, due to ambient sources of PAH exposure. Thus, smoking cessation was only expected to result in reduction of urinary 1-OHP. Urinary 1-OHP levels were significantly correlated with the amounts of cigarettes smoked, as assessed by the questionnaire (Spearman’s correlation coefficient, r=0.23, P=0.03). This study suggested that urinary 1-OHP can be a potentially useful biomarker of smoke.