Daily vitamin D in addition to calcium supplementation reduces falls and fractures in older women. However, poor adherence to therapy is a common clinical problem. To examine the effects of supervised oral 3‐monthly vitamin D therapy on falls, muscle strength, and mobility, we conducted a 9‐month randomized, double‐blind, placebo‐controlled trial in 686 community‐dwelling ambulant women aged over 70 years. Participants received either oral cholecalciferol 150,000 IU every 3 months (n = 353) or an identical placebo (n = 333). All participants were advised to increase dietary calcium intake. Falls data were collected 3‐monthly. At baseline, 3, 6, and 9 months, muscle strength was measured by a handheld dynamometer and mobility by the Timed Up and Go (TUG) test. Serum 25 hydroxyvitamin D (25OHD) was measured in a subgroup of 40 subjects. Mean age at baseline was 76.7 ± 4.1 years. The average serum 25OHD value at baseline was 65.8 ± 22.7 nmol/L. By 3, 6, and 9 months after supplementation, 25OHD levels of the vitamin D group were approximately 15 nmol/L higher than the placebo group. Calcium intake did not change significantly between baseline (864 ± 412 mg/day) and 9 months (855 ± 357 mg/day). Faller rates in the two groups did not differ: vitamin D group, 102 of 353 (29%); placebo group, 89 of 333 (27%). At 9 months, compared to placebo or baseline, muscle strength, and TUG were not altered by vitamin D. In conclusion, oral cholecalciferol 150,000 IU therapy administered 3‐monthly had neither beneficial nor adverse effects on falls or physical function. These data together with previous findings confirm that intermittent large doses of vitamin D are ineffective or have a deleterious effect on falls. Thus despite adherence issues with daily vitamin D replacement, an intermittent, high‐dose vitamin D regimen cannot be supported as a strategy to reduce falls and fractures. © 2012 American Society for Bone and Mineral Research