Several studies indicate that glucose tolerance improves and lipid levels decline in the elderly after supplementation with Cr-rich brewer's yeast or inorganic Cr. Other studies report equivocal results or no changes. Interpretation of these investigations is hampered by 1. Lack of a marker to identify Cr-deficient people 2. Artifactually high levels of dietary and body Cr, owing to inadequate analytic techniques and 3. The interplay of chronic health problems, medications, institutionalization, and dietary practices. Investigators have studied the effects of aging on Cr in the body. In the rat, tissue retention of 51Cr decreases, and organ distribution changes with age. In humans, plasma Cr levels of healthy elderly subjects are not different from those of young adults. There is no evidence of malabsorption in aged humans or animals. Nevertheless, higher urinary Cr losses are reported in elderly people. These data suggest that Cr retention may decrease with aging and that aging may alter Cr metabolism. Diets of many healthy elderly people contain less than 30 micrograms Cr. Two elderly men living under controlled conditions maintained Cr balance with 37 micrograms/d. However, these levels may be insufficient during the stresses and illnesses associated with aging.