The pharmacokinetics of norfloxacin after intravenous (IV) and oral (PO) administration in lambs (n=5) and adult sheep (n=5) were studied. After IV administration (10 mg.kg‐1) plasma concentrations were best fitted by a three‐compartment open model in both age groups. Distribution volumes were significantly larger in lambs (approximate 4.0 fold difference between 4 week old and adult sheep). There was no significant difference (p<0.05) between the groups in terms of elimination half‐life but plasma clearance was significantly higher in lambs. Norfloxacin was poorly absorbed after oral administration (60 mg•kg‐1) in sheep (F=4.04%). Mean oral bioavailavility was 73.51% in lambs (30 mg.kg‐1). Norfloxacin elimination was faster in lambs after oral administration. MRTtwas significantly prolonged in both age groups when compared with the respective data for IV administration.