It is unclear whether vitamin D supplementation reduces risk of falls, and results from randomized controlled trials (RCTs) are conflicting.To determine whether 2000 IU/day of supplemental vitamin D3 decreases fall risk.VITamin D and OmegA-3 TriaL (VITAL) is a double-blind, placebo-controlled RCT including 25,871 adults, randomized November 2011-March 2014 and treated for 5.3 years (median).Nationwide study.Men ≥50 and women ≥55 years (mean age 67.1 years) without cancer or cardiovascular disease at baseline.Vitamin D3 (cholecalciferol; 2,000 IU/day) and/or omega-3 fatty acids (1 g/day) or respective placebos in a 2X2 factorial design.Two or more falls, falls resulting in a doctor or hospital visit.Baseline serum total 25-hydroxyvitamin D [25(OH)D] level was 77 nmol/L; characteristics were well-balanced between groups. Numbers of participants with ≥2 falls were similar between active and placebo groups (9.8% vs. 9.4%). Over 5 years, there were no differences in the proportion having ≥2 falls (OR=0.97; 95% CI, 0.90-1.05, p=0.50), falls resulting in a doctor visit (OR=1.03; 95% CI, 0.94-1.13, p=0.46) or resulting in a hospital visit (OR=1.04; 95% CI, 0.90-1.19, p=0.61) between groups. Results did not differ between those with baseline 25(OH)D <50 vs. >50 nmol/L or other cutpoints.Daily supplemental vitamin D3 vs. placebo did not decrease fall risk in generally healthy adults not selected for vitamin D insufficiency. This large RCT does not indicate that supplemental vitamin D should be used for primary prevention of falls in the U.S. population.