Reduced glomerular filtration rates (GFR less than 90 ml/min/1.73 sq m) were found in 21 of 57 lead workers in whom excessive body lead burdens had been shown by the urinary excretion of more than 1,000 microgram of lead per day during an edetate disodium calcium lead-mobilization test. In 12 patients, renal biopsies confirmed the diagnosis of occupational lead nephropathy and further excluded other possible causes of kidney disease. Glomerular and tubular immunoglobulin deposition in seven of eight biopsy specimens examined by immunofluorescent microscopy raises the possibility that an autoimmune response may contribute to the interstitial nephritis of occupational lead nephropathy. The GFR increased 20% or more in four of eight patients treated with 1 g of edetate disodium calcium three times weekly for from six to 50 months, further confirming the diagnosis of lead nephropathy and indicating a favorable response to prolonged chelation therapy.