N-Acetyl-beta-D-glucosaminidase (NAG) activity and beta 2-microglobulin (beta 2-m) concentration were measured in the urine of inhabitants of a cadmium-polluted area (Cd), including patients with, or suspected, "itai-itai" disease and control subjects. Urinary NAG activity increased with increasing beta 2-m concentration up to about 100 U/g creatinine; above this value the NAG activity did not increase with increasing beta 2-m concentration. Urinary NAG activity thus represents another useful indicator of renal tubular damage caused by Cd poisoning since the mechanisms for the excretion of NAG and beta 2-m into urine are thought to be different.