Because of evidence implicating oxidative stress in multiple sclerosis pathogenesis, it has been postulated that high levels of urate, a potent antioxidant, could reduce risk or favorably influence disease progression. We conducted a prospective study to determine whether serum urate levels contribute to prediction of multiple sclerosis risk. Analyses included 31 cases with blood collected a median of 1.9 years before multiple sclerosis onset from the Nurses' Health Study and Nurses' Health Study II cohorts, and 42 cases with collection a median of 14.5 years before onset from the Kaiser Permanente Northern California health plan cohort. Relative risks were estimated by unconditional logistic regression, including 26 controls in the Nurses' cohorts and 130 controls in the Kaiser cohort. In analyses including only cases in the Nurses' cohorts where blood was collected shortly before onset, there was a trend toward a lower risk of multiple sclerosis among individuals with higher serum urate, but the association was not significant (multivariable relative risk 0.52, 95% CI 0.22, 1.20, p value 0.13). In contrast, there was no evidence of a decline in risk with increasing serum urate in the Kaiser cohort where there was a longer period of time between blood collection and onset (multivariable relative risk 1.36, 95% CI 0.87, 2.14, p value 0.18). The results of this study suggest that serum urate is not a strong predictor of MS risk. This lack of association is consistent with the interpretation that the lower urate levels among multiple sclerosis cases are a consequence rather than a cause of the disease.