Oral contraceptive (OC) use has been associated with alterations in carbohydrate metabolism. We examined the effect of OC use on the risk of diabetes among Chinese women. A nested case-control study was conducted among 57,130 women screened for diabetes at enrollment for the Shanghai Women's Health Study, a population-based cohort study of Chinese women aged 40-70 years in Shanghai, China. Included in this study were 259 women newly diagnosed with diabetes and 2072 age-matched controls (8 controls per case), randomly selected from women who tested negative for urine glucose. Multivariate-adjusted odds ratios (OR) and 95% confidence intervals (CI) were used to measure the strength of the association between OC use and diabetes risk. Overall, OC use was not associated with the risk of diabetes. Stratified analysis by menopausal status revealed a dose-response relationship between the duration of OC use and the risk of diabetes among premenopausal women (p for trend = 0.02), with a 3.2-fold elevated risk observed among those who used OC longer than 1 year. Risk of diabetes diminished with increasing time since last OC use (p = 0.02). Use of intrauterine devices was associated with a reduced risk of diabetes in both pre- and postmenopausal women (OR = 0.67, CI: 0.48-0.93). These findings suggest that recent use (within 5 years) and continued use (>1 year) of OCs may increase the risk of diabetes among Chinese women. However, the attributable risk for diabetes among OC users in the general population, if confirmed by further studies, appears to be small.