Lacto-ovo-vegetarian women fifty to eighty-nine years of age lost 18 per cent bone mineral mass while omnivorous women lost 35 per cent. This study established that this difference could not be explained by a greater bone density in the lacto-ovo-vegetarians during the third, fourth, and fifth decades of life. The possibility of higher sulfur content in the meat-containing diet, the effect of excess phosphorus, and the effect of an acid-ash diet are discussed. From the standpoint of a general survey, comsumption of calcium-containing foods was not appreciably different in the two groups. It is, therefore, concluded that lacto-ovo-vegetarian diet may be beneficial in extended protective health care in terms of defense against, or control of, bone mineral loss in the later years of a woman's life.