Urinary incontinence (UI) is a common disorder among older women that greatly affects quality of life. Emerging evidence from observational studies links vitamin D insufficiency with UI. Prior to a larger intervention trial of vitamin D among older women with low serum vitamin D levels and urgency UI, we propose a pilot study in 100 older women comparing weekly, oral vitamin D3 50,000 IU to placebo. We hypothesize that adequate vitamin D supplementation will improve UI symptoms in older women with vitamin D deficiency. Changes in UI-episodes will be assessed by a 7-day bladder diary and other validated symptom measures administered at baseline and after 12-weeks of intervention. Serum calcium and 25(OH)D levels will be monitored. The expected outcomes will provide new knowledge regarding the impact of vitamin D supplementation on UI symptom improvement and inform a larger, randomized controlled clinical trial involving vitamin D supplementation.