The pharmacokinetics of ofloxacin, a fluoroquinolone widely used in the treatment of bacterial infections, may be different according to age, owing to the biological differences that exist between an elderly organism and a young subject, especially as regards the renal and the hepatic function. In our study the pharmacokinetics of ofloxacin in 12 elderly patients was found to be different from those of 12 healthy young volunteers. The elimination half-life (t1/2) was slightly shorter in the young subjects than in the elderly: 6.2 (0.9)h against 8.5(1.2)h respectively. The oral total clearance was lower in the geriatric patients compared to the young healthy volunteers: 83.3(16.6) ml/min in the first group, and 23.3(33.3) ml/min in the second group. AUC and peak plasma concentration in elderly exceeded those noted in young healthy volunteers. The results of this study suggest that, compared with younger subjects, older patients experience delayed elimination of ofloxacin. It would be reasonable, from a pharmacokinetic point of view, to limit the dose of ofloxacin in patients more than 75 years old, at least to one half of that given to younger patients.