This study reports the cadmium concentration and histopathology of kidney tissue from 29 patients with clinical findings that motivated a diagnostic percutaneous kidney biopsy and/or a history of possible exposure to cadmium. Cadmium was found in all specimens examined including those from controls. In the patients, the mean cadmium concentration was 12.9 (0.6-45.0) micrograms cadmium per g wet kidney tissue. The highest concentrations (30-45 micrograms/g) were found in three patients with morphological and clinical findings of tubulo-interstitial damage. Patients with signs of tubulo-interstitial disease had higher mean cadmium concentrations than those with glomerular changes, and patients with normal blood pressure had higher concentrations than those with diastolic hypertension. In a control group of 22 autopsies, the mean cadmium concentration was 8.7 (2.9-22.4) micrograms/g. The mean difference between the right and the left kidney was 2.3 (0.9-9.6) micrograms/g. Laboratory findings in patients with cadmium nephropathy were nonspecific. Thus, in patients with interstitial nephritis and cadmium exposure, a biopsy for the analysis of kidney cadmium concentration may be motivated. The combination of morphological and clinical findings of interstitial nephritis and a high concentration of cadmium in biopsied kidney tissue indicates cadmium nephropathy.