BACKGROUND: Glomerular filtration rate (GFR) decline with age increases the risk of inappropriate dosing of drugs. We investigated the determinants and the mortality associated with the use of drugs that are contraindicated or require dose adjustment according to kidney function among the community-dwelling elderly. METHODS: The Three-City population-based study included 8701 participants >/=65 years from 1999 to 2001. Exposure to the risk of inappropriate drug dosage was defined as reported use of either a contraindicated drug or one requiring dose adjustment according to the individual baseline glomerular filtration rate estimated (eGFR) with the Modification of Diet in Renal disease study equation. Six-year mortality was analysed using Cox models adjusted for several sociodemographic, biologic and clinical risk factors. RESULTS: The overall percentage of exposure to the risk of inappropriate drug use was 13.3% (contraindication, 0.8%): it was 52.5% (4.5%) in those with an eGFR of 30-59 and 96% (48%) in those <30 mL/min/1.73 m(2). Antihypertensive agents, fibrates and psycholeptics accounted for most of the drugs with dosing recommendations and antidiabetic agents and antihistamines for those contraindicated. Individuals at risk were more likely to be men, older, and under treatment for hypertension or hypercholesterolemia. Exposure to either risk was independently related to higher all-cause mortality (hazard ratio 1.4, 95% confidence interval 1.0-1.9) in participants with eGFR <60 mL/min/1.73 m(2). CONCLUSIONS: Contraindicated drug prescription was uncommon but >10% of the population took drugs requiring renal dosing adjustments. Regular monitoring of eGFR may prevent excess mortality associated with inappropriate drug prescription in the elderly.