Low vitamin D levels are common among patients with Parkinson's disease (PD). Experimental evidence further suggests that vitamin D may be protective against PD. The objective of this study was to prospectively assess the association between serum 25-hydroxyvitamin D and PD among 12,762 participants of the Atherosclerosis Risk in Communities Study cohort. Serum samples were collected in 1990-1992, and 25-hydroxyvitamin D was measured by liquid chromatography mass spectrometry. A total of 67 incident PD cases were identified through December 31, 2008. The median length of follow-up was 17 years. We used Cox proportional hazards models to obtain hazard ratios and 95% confidence intervals, adjusting for age, sex, and race. We did not find any association between serum 25-hydroxyvitamin D concentrations and PD risk, regardless of how serum 25-hydroxyvitamin D was modeled. Compared with participants with serum 25-hydroxyvitamin D < 20 ng/mL, the hazards ratio for PD was 1.05 (95% confidence interval, 0.58-1.90) for 20-30 ng/mL and 1.14 (95% confidence interval, 0.59- 2.23) for ≥30 ng/mL. Similar results were obtained in sensitivity analyses that included white participants only and that were stratified by the length of follow-up. This prospective study lends no support to the hypothesis that vitamin D may reduce the risk of PD. © 2016 International Parkinson and Movement Disorder Society.