Many people taking aspirin or Tylenol every day do not even consider chronic renal failure as a possible risk. However, a recent study (N Engl J Med 2001;345(25):1801-1808) shows that there is reason for concern. The study was conducted on 926 patients with newly diagnosed renal failure and 980 control subjects. It used logistic-regression models to estimate the relative risks associated with the use of various analgesics. The study concluded that aspirin or Tylenol were used regularly by 37% and 25%, respectively, of the patients with renal failure and 19% and 12% of the controls. Regular use of either drug was associated with an increase by a factor of 2.5 in the risk of chronic renal failure, and the risk rose with increasing cumulative lifetime doses. However, the study found that the risk of developing kidney failure from either drug was minimal in people without pre-existing kidney disease.