Elevated urinary trehalase activity was observed in the inhabitants of the Jinzu River basin. Urinary trehalase activity was correlated with other urinalysis components, such as beta 2-microglobulin, glucose, amino nitrogen, and cadmium, of which a high level was observed in cadmium-polluted areas as compared with the reference area. Renal trehalase is specifically localized in tubular brush borders [M. Nakano, J. Histochem. Cytochem., 30 (1982) 1243-1248]. From these results it is inferred that tubular brush-border damage occurs in inhabitants of the Jinzu River basin.