Renal function was studied in 145 asymptomatic male heroin addicts admitted to a methadone detoxification program. The mean duration of addiction was ten years. Three patients had protein excretion greater than 150 mg/24 hr; in one of these, membranous glomerulonephritis was found. All except one had normal creatinine clearance. Hypertension was present in 2.7%. This study does not support the concept that heroin addiction is associated with a high prevalence of renal disease.