In Tunisia, where new oral anticoagulants and warfarin are not available yet, acenocumarol continues to be underused in the elderly patients with atrial fibrillation (AF), mainly due to the over estimation of the bleeding risk and the difficulties to comply with treatment.The aim of the present prospective study was to investigate whether age influences the quality of anticoagulation by acenocumarol.Sixty patients having non-valvular atrial fibrillation on acenocumarol were followed up prospectively in our department of cardiology during one year. They underwent regular PT and INR measurements. Patients were divided into two groups: younger than 65 years (group 1: 40%) and older than 65 years (group 2: 60%).The thromboembolic and hemorrhagic risk were significantly higher in elderly compared to younger patients (CHA2DS2 VASc score=3.43±1.18 vs. 2.09±1.23 P=0.0001; HASBLED score=2.16±0.87 vs. 1.37±0.77 P=0.001). The mean INR and the dose of acenocumarol did not differ between both groups (mean INR=2.58±0.29 in group 1 versus 2.7±0.56 in group 2, P=0.22; mean dose=2.48±0.96mg versus 2.24±0.88, P=0.35). The mean TTR was also similar in the two groups: 56%±16 in the non-elderly group and 51%±16 in the elderly group (P =0.24). Hemorrhagic complications were similar in both groups (5% versus 8.3%; P=0.87).Our results suggest that in elderly AF patients, oral anticoagulation with acenocumarol has similar safety and efficiency than in younger AF patients.