Vitamin D deficiency is associated with osteoporosis, poor muscle strength, falls, and fractures. The relationship between serum vitamin D concentrations and mortality in older community-dwelling women has not been well characterized. We hypothesized that women with lower 25-hydroxyvitamin D (25[OH]D) concentrations were at higher risk of mortality. We examined the association between serum 25[OH]D concentrations and all-cause mortality in a prospective, population-based study of 714 community-dwelling women, aged 70 to 79 years, the Women's Health and Aging Studies I and II in Baltimore, Md. The studies were originally designed to evaluate the causes and course of physical disability in older women living in the community. Vital status was determined through follow-up interviews and matching with the National Death Index. During a median of 72 months of follow-up, 100 (14%) of 714 women died. Women in the lowest quartile of 25(OH)D (<15.3 ng/mL or 38.2 nmol/L) were at higher risk of death (hazards ratio, 2.45; 95% confidence interval, 1.12-5.36; P = .02) compared to women in the highest quartile (>27.0 ng/mL or 67.4 nmol/L) of 25(OH)D in a multivariate Cox proportional hazards model adjusting for demographics, season, and conventional risk factors. Older community-dwelling women with low 25(OH)D levels are at an increased risk of death.