Polycyclic aromatic hydrocarbon (PAH) exposure and oxidative stress from such and other exposures have been associated with breast cancer in some studies. To further evaluate the role of PAH metabolites and oxidative stress on the development of breast cancer, we conducted a nested case-control study in the Shanghai Women's Health Study. We measured urinary 1-hydroxypyrene and 2-naphthol as PAH metabolites and urinary levels of 8-hydroxy-2'-deoxyguanosine and malondialdehyde as oxidative stress biomarkers in 327 breast cancer cases and 654 controls in the Shanghai Women's Health Study. Information on demographic characteristics, past medical history, lifestyles, history of menstruation, pregnancy history, eating and drinking habit, history of residence, employment history, family history, husband's information, and physical activity were collected by a self-administered questionnaire. The mean age was 52.3 in breast cancer cases (n = 354) and 52.5 in controls (n = 708). Age at menarche (P = 0.04), months of breast-feeding the first baby (P = 0.05), and grade of education (P(trend) < 0.01) were significantly different between cases and controls. No association was observed for PAH metabolites and the oxidative stress biomarkers of urinary malondialdehyde and 8-hydroxy-2'-deoxyguanosine and risk of breast cancer. This nested case-control study provides no evidence of association between PAH exposure and oxidative stress and risk of breast cancer in Shanghai women.