Cadmium concentrations in whole blood have been determined in normal control subjects, in patients with untreated essential hypertension or with treated essential hypertension, and in those with acute or chronic renal disorders. High cadmium concentrations were not found in the patients with untreated essential hypertension. Most tobacco smokers were found to have high blood cadmium concentrations. When the mean cadmium concentrations from each group of patients were compared with those of the control subjects no significant differences were found. When the four groups were divided into smokers and non-smokers, however, a significantly higher mean value was found for the non-smoking renal patients in comparison with the non-smoking normal subjects. The marked increases in blood cadmium concentration in the patients with renal disorders may be attributed to impaired excretion.