Numerous reports of chronic renal disease in patients who habitually use phenacetin-containing compounds to excess have aroused considerable controversy over the possible relationship between phenacetin, alone or in combination with other analgesics, and the occurrence of renal damage. Between 1961 and 1964, we have seen 23 patients with severe renal failure and a history of prolonged, excessive use of phenacetin-containing compounds. In all instances the clinical and laboratory data were compatible with "phenacetin nephritis" as described in Europe and Australia and recently in the United States and Canada. This report evaluates the findings in the 23 cases and cautions against the use of phenacetin, particularly in patients with impaired renal function.