Context: Vitamin D is known to influence muscle health. A reduction in muscle mass increases the risk of functional limitations among older individuals. Objective: The aim of this study was to examine the relationship between vitamin D status and functional limitations. Design, Setting, and Participants: Two independent cohorts of the Longitudinal Aging Study Amsterdamwereused. Participantswereaged65 to 88 years (older cohort,n1237; baseline 1995) and 55 to 65 years (younger cohort, n 725; baseline 2002). Main Outcome Measures: Questions on the ability and degree of difficulty to perform 6 functions of daily life were asked. Results: Of the participants, 56% in the older cohort and 30% in the younger cohort had 1 limitation. VitaminDdeficiency (25-hydroxyvitaminDlevel of20 ng/mL)comparedwith the value in the reference group (30 ng/mL)wasrelated to the presence of functional limitations at baseline (odds ratio [OR] 1.7; 95% confidence interval [CI], 1.2-2.5 and OR 2.2; 95% CI 1.3-3.7 for the older and younger cohorts, respectively). In the older cohort, vitamin D deficiency was associated with an increase in limitations at 3 years (OR 2.0; 95% CI, 1.1-3.5), whereas vitamin D deficiency in the younger cohort was associated with an increase in limitations at 6 years (OR 3.3; 95% CI, 1.1-10.1). Analyses were adjusted for confounders. Conclusion: Vitamin D status is associated with functional limitations cross-sectionally and longitudinally in individuals aged 55 to 65 years and those 65 years and older. The possible association of vitamin D with functional limitations is present after a shorter follow-up time in the oldest age group compared with the younger age group. Copyright © 2013 by The Endocrine Society.