A protective effect of vitamin D on risk of multiple sclerosis (MS) has been proposed, but no prospective studies have addressed this hypothesis. Dietary vitamin D intake was examined directly in relation to risk of MS in two large cohorts of women: the Nurses’ Health Study (NHS; 92 253 women followed from 1980 to 2000) and Nurses’ Health Study II (NHS II; 95 310 women followed from 1991 to 2001). Diet was assessed at baseline and updated every 4 years thereafter. During the follow-up, 173 cases of MS with onset of symptoms after baseline were confirmed. The pooled age-adjusted RR comparing women in the highest quintile of total vitamin D intake at baseline with those in the lowest was 0.67. Intake of vitamin D from supplements was also inversely associated with risk of MS; the RR comparing women with intake of = 400 IU/day with women with no supplemental vitamin D intake was 0.59. No association was found between vitamin D from food and MS incidence.