Cadmium is widely used in industry, causing exposure of workers and environmental pollution because of its persistence in the biosystems. Its very long half-life in the human organism causes its accumulation over the lifetime in liver and kidneys. Cadmium ions have a high affinity for tissue thiols, induce the synthesis of a carrier cysteine-rich polypeptide called metallothionein, and impair proteoglycan metabolism. Significant renal effects include early tubular nephropathy manifested by proteinuria, amino aciduria, glucosuria, phosphaturia, and calcium wastage. Chronic sequels include decrease in the glomerular filtration rate and increased risk of kidney stone disease. Biological monitoring of cadmium absorption includes determination of urinary cadmium and of low molecular weight marker proteins, such asβ2-microglobulin or retinol binding protein, the tubular reabsorption of which is impaired before a frank proteinuria.