Percutaneous biopsies were performed in 14 unselected addicts, ranging in age from 21 to 52 years, who had no manifest cardiac, hepatic or sickle-cell disorder. Urinary findings ranged from normal to a trace of protein with a few red blood cells and a few white blood cells; Australian antigen was negative. All were normotensive and blood chemistries were within normal range. By light microscopy, 12 cases exhibited slight nonspecific increase in mesangium. Three cases had, on immunofluorescent studies, mesangial deposits -predominantly of IGm – and two cases had basement membrane deposits of IGg. Electron microscopy revealed focal foot process fusion, increase in mesangium and small electron-dense deposits in six cases. In view of the propensity of addicts to develop variegated renal disorders, the asymptomatic renal lesions herein described may represent early manifestation of kidney disease as a consequence of drug usage and deserve further investigation.