Analgesic nephropathy is characterized by poor clinical symptoms. Abnormal urinary findings are rare. The disease is usually discovered if advanced renal damage has occurred with elevated serum creatinine, papillary necrosis, microhematuria and renal colics. There is abundant evidence, that abuse of phenacetin leads to analgesic nephropathy. Aspirin may have only an additive effect with phenacetin in causing renal damage. The primary medullary changes caused by phenacetin or one o f its metabolites are: Interstitial fibrosis, thickening of tubular basement membrane, loss of tubular epithelium and finally destruction of the loops of Henle. The consequence of these histological changes is a loss of urinary concentrating ability, one of the earliest findings in analgesic nephropathy. Inflammatory cell infiltration and involvement of the renal cortex with corresponding functional defects are secondary. Intravenous pyelography reveals in this stage of the disease symmetrically shrunken kidneys with a smooth wavy outline, whereby in contrast to the pyelonephritic changes the prtrusions correspond with the renal calyces. Papillary necrosis with the typical "halo shacow" in the pyelogramm rarely leads to the discovery of the disease.--Cessation of phenacetin consumption is usually associated with stabilization of renal funciton in patients with serum creatinine levels below 1.5 mg percent; with elevated serum creatinine there is a slow progression of the disease.--Analgesic nephropathy may be prevented by high fluid intake and avoidance of more than 150 g phenacetin per year respectively 0.5 g per day. Coffein, a constituent of many preparations, has a protective effect only with sufficient fluid intake.--The socio-economic importance of the analgesic nephropathy is given by the fact, that in the German Federal Republic 10 percent and in Australia even 20 percent of the patients requiring recurrent dialysis suffer from analgesic nephropathy. The following measures have been found to be effective in order to reduce phenacetin abuse: 1. Preparations containing phenacetin subject to prescription. 2. No advertising in newspapers and television. 3. Detailed information about kidney damaging effect of phenacetin on each packaging.