Vitamin D deficiency is now recognized as a significant health problem for middle-aged and older adults. Vitamin D deficiency exacerbates osteoporosis and causes the bone disease, osteomalacia. Vitamin D deficiency increases risk of skeletal fractures. It is well known that the ultraviolet B portion of the solar spectrum is responsible for the cutaneous production if vitamin D3. It has been estimated that approximately 90 to 95% of most people's vitamin D requirement comes from their casual exposure to sunlight. However, people above the age of 50 years do not get adequate exposure to sunlight placing them at risk for vitamin D deficiency. The goal of this program is to determine the feasibility of developing ultraviolet B light sources that can be used in a nursing home setting or in an individual home for promoting the cutaneous production of vitamin D3. This will be accomplished by using a whole body ultraviolet B light source and a portable partial body ultraviolet B home device unit. The goal will be to test the effect of exposure to varying doses of whole body and partial body ultraviolet B radiation from these prototype commercial devices to determine their effect on raising the blood level of vitamin D and 25-hydroxyvitamin D, the major circulating form of vitamin D that is used to determine the vitamin D status. This study addresses an issue crucial to the successful commercial development of ultraviolet B radiation sources that can be placed in nursing homes or in an individual home for the therapeutic purpose of producing vitamin D3.