Cadmium, copper, lead, manganese, and selenium concentrations and glutathione peroxidase (EC 1.11.1.19) activity have been determined in human kidney cortex specimens obtained at autopsy. Trace metal concentrations for each specimen were determined in the same digest, while glutathione peroxidase activity was assayed in tissue collected at a site adjacent to that selected for the trace metal determinations. Glutathione peroxidase activities were determined with two substrates, hydrogen peroxide and t-butylhydroperoxide. The effects of age, smoking history, sex, race, and blood pressure on kidney cortex trace metal levels and glutathione peroxidase activity were investigated. Mean kidney cortex cadmium concentration was found to be significantly higher in smokers than in nonsmokers (p=0.010). In addition, the mean kidney cortex lead concentration of hypertensive individuals was found to be significantly higher than that of non-hypertensive individuals (p=0.017), Glutathione peroxidase activities utilizing hydrogen peroxide substrate were inversely correlated to kidney cortex manganese levels (p=0.004).