BACKGROUND: Adequate vitamin D and calcium nutrition play a critical role in the maintenance of musculoskeletal health and are considered the first step in osteoporosis treatment. ROUNDTABLE DISCUSSION: In February 2008 Merck Sharp & Dohme sponsored a 2-day, evidence-based expert panel on the benefits of vitamin D for the patient with osteoporosis and the role of vitamin D in combination with antiresorptive therapy for the management of osteoporosis. One of the primary objectives of the meeting was to review new data on the optimal serum 25-hydroxy vitamin D [25(OH)D] levels. The symposium was attended by 29 researchers and clinicians from Europe and the Middle East. The discussion focused on optimizing vitamin D and calcium nutrition and reducing falls and fractures in osteoporotic patients. CONCLUSIONS: Current evidence and expert opinion suggests that optimal serum 25(OH)D concentrations should be at least 50 nmol/L (20 ng/mL) in all individuals. This implies a population mean close to 75 nmol/L (30 ng/mL). In order to achieve this level, vitamin D intake of at least 20 microg daily is required. There is a wider therapeutic window for vitamin D than previously believed, and doses of 800 IU per day, regardless of sun exposure, season or additional multivitamin use, appear to present little risk of toxicity. Apart from fracture and fall prevention, optimization of vitamin D status may also have additional general health benefits. Based on newly emerging data regarding calcium supplementation, and recommendations for increased vitamin D intake, the current recommendations for calcium intake in postmenopausal women may be unnecessarily high. In addition to vitamin D and calcium, treatment of patients with osteoporosis at high risk of fractures should also include pharmacologic agents with proven vertebral and non-vertebral fracture efficacy.