Kidney biopsies often show accumulation of lipids or lipidlike material. Evidence has been provided that lipids can directly initiate and contribute to the progression of glomerular and tubulointerstitial lesions. In this study we describe a renal lipidosis occurring in patients with a positive history of narcotic abuse who were enrolled in a methadone substitution program. All 3 patients presented with proteinuria (2.5-20 g/d) and impaired renal function. Renal biopsy revealed a pronounced extracellular and intracellular deposition of lipidlike material in the glomerular, interstitial, and tubular compartments. Known causes of lipid storage could be excluded clinically and morphologically. We consider this to be a distinct renal lipidosis associated with narcotic abuse, methadone intake, or intravenous abuse thereof.