Calcium and vitamin D are essential for bone maintenance and for treatment-induced bone augmentation. Deficiencies of both nutrients are very common in the age group most afflicted by osteoporosis. Calcium enhancement of estrogen's effects now have been clearly demonstrated. Additionally, all currently approved bone active agents have been tested only in the presence of extra calcium, and newer anabolic agents create a skeletal need for mineral that will require even higher levels of calcium repletion. Prudent nutritional support for osteoporosis prevention and treatment consists of 30 to 40 mmol Ca/d together with sufficient vitamin D to maintain serum 25(OH)D levels above 80 nmol/L (i.e., approximately 25 microg vitamin D/d).