One of the complications of bedfastness, extended inactivity, and a common accompaniament of advancing age is bone demineralization accompanied by pathologic fractures. The objective of the study already in progress, and for which support for continuation is requested, is to evaluate the efficacy of three compounds in preventing the onset of osteoporosis or in reversing the process of demineralization. The compounds being evaluated (sodium fluoride, inorganic phosphate, and the anabolic steroid oxymetholone) may be classed among those having relatively few safety problems (in contrast to calcitonin, diphosphonates, etc). Because the x-ray densitometric data and biochemical monitoring after six months of treatment have shown encouraging results we propose to extend the duration of treatment to 48 months instead of the originally-planned 18 months.