Internal exposure of university students to polycyclic aromatic hydrocarbons(PAHs)was assessed through urinary PAHs metabolites. Eight monohydroxylated PAHs(OH-PAHs)were detected with high performance liquid chromatography (HPLC). The detectable frequencies were 59%-100% for different analytes. Major components in the subjects' urine were 2-hydroxynaphthalene(2-OHNap, 0.60 μg/mmol creatinine), followed by hydroxyphenanthrene(ΣOH-Phe, 0.38 μg/mmol cre-atinine)and 2-hydroxyfluorene(2-OHFlu, 0.25 μg/mmol creatinine). Excretion of 1-hydroxypyrene(1-OHPyr, 0.08 μg/mmol creatinine)was almost one order of magnitude lower than the 2-OHNap level in the urine samples. Phenanthrene can be metabolized to five monohydroxy metabolites in human urine. In the present study, 1-or 9-hydroxyphenanthrene(1-or9-OHPhe)was the dominant component(79%), followed by 2-+3-OHPhe(18%)and 4-OHPhe(3%). The study indicates that 1-OHPyr may not be a good marker for total PAHs exposure, and monitoring of 2-OHNap, 2-OHFlu, 1-or 9-OHPhe and 1-OHPyr as multiple biomarkers are more suitable than only using 1-OHPyr. The levels of OH-PAHs detected in urines of students living in Shanghai are higher those of people in other countries or regions. The concentrations of urine OH-PAHs are directly related to the exposure to PAHs in the environment, indicating that Shanghai residents are at high health risk.