We report five patients who have taken inorganic germanium preparations over a prolonged period. In all cases, the renal function deteriorated with no proteinuria or hematuria. Histological examination of the kidneys showed widespread tubular degeneration and interstitial fibrosis with minor glomerular abnormalities. Most patients had gastrointestinal symptoms such as vomiting, anorexia and weight loss; one patient had peripheral neuropathy and myopathy. A considerable amount of germanium was detected in the hair or nails of these patients. These cases clearly show that abuse of inorganic germanium compounds can induce renal damage with various extrarenal manifestations.