Eight patients with serious chronic renal disease and a long history of heavy use of analgesics containing phenacetin (acetophenetidin) arc described. Admitted acetophenetidin consumption ranged from 1 to 5 gm daily over many years with an ingestion pattern suggesting habituation or addiction. Chronic headache was the outstanding symptom. Findings included hyperazotemia, moderate to severe anemia, mild hypertension, minimal proteinuria, and minor abnormalities in the urinary sediment. Six patients had bacteriuria. Two had "secondary" renal tubular acidosis. Three died of uremia. Pathologic findings were severe papillary necrosis without extensive polymorphonuclear exudate, interstitial fibrosis with remarkable atrophy of tubules and peritubular capillaries in the medulla, focal areas of tubular atrophy in the cortex, and increase in round cells and fibrous tissue in the interstitium. These changes were felt to be unique, recognizable, and different from those caused by pyelonephritis alone.