Approximately 1000 urine samples were collected from the general adult U.S. population, and analyzed for cadmium, beta2-microglobulin, specific gravity, and creatinine. The distributions of urinary cadmium and beta2-microglobulin levels were quantified for use as benchmarks against which the effects of environmental cadmium exposure may be measured. Urinary cadmium is significantly higher in females than males, and increases significantly with age. Urinary beta2-microglobulin is significantly higher in males than females, is probably related to age, and does not significantly increase with increased urinary cadmium (at the levels found). Since urinary creatinine is lower in females than males and is a function of age, specific gravity is concluded to be the most straightforward and practical parameter to use in urine concentration adjustment.