Vitamin D has a wide range of biological effects beyond calcium and bone metabolism, and low 25-hydroxyvitamin D levels have been associated with many disease states in recent years, including cardiovascular disease, diabetes, infections and cancer. Association studies of vitamin D are notoriously prone to confounding and to reverse causality, however, and current intervention trial data for non-skeletal indications have been disappointing. Vitamin D is indicated for treatment of osteomalacia in older people, falls prevention in institutionalized older people, and as adjunctive therapy for osteoporosis. Large trials currently underway will ascertain whether potentially beneficial effects of vitamin D supplementation on all-cause mortality in older people are borne out.