It has become increasingly apparent that the pathogenesis of osteoporosis is complex, poorly understood, and ill-defined. Calcium deficiency and/or calcium malabsorption and the homeostatic response to this biological insult may ultimately prove to be one of the pivotal factors in conditioning or modulating the skeletal response to senescence. Until we know more about the prevention and potential reversibility of age-related changes in bone cell function, hormonal secretion and metabolism, and dietary patterns that prove deleterious to skeletal health, clinicians will be confronted with an ever-increasing population of aging, fracture-prone, osteoporotic patients. Because calcium supplements improve the calcium balance of perimenopausal and postmenopausal women and because improvements in calcium balance can be correlated with increased skeletal mass, it appears desirable to focus our efforts on diets and/or calcium supplements that guarantee an adequate supply of this essential mineral. Because calcium replacement may simply retard bone resorption and may not restore bone already lost by the fracture-prone, osteoporotic female, dietary analyses and appropriate modification of calcium intakes should be made at least in the third and fourth decades of life, with the goal of retarding the inexorable loss of skeletal tissue as early as possible.