The pharmacokinetic properties of marbofloxacin, a third generation fluoroquinolone, were investigated in six cats after single intravenous (IV) and repeat oral (PO) administration at a daily dose of 2 mg/kg. Marbofloxacin serum concentration was analysed by microbiological assay using Klebsiella pneumoniae ATCC 10031 as micro-organism test. Serum marbofloxacin disposition was best described by bicompartmental and mono-compartmental open models with first-order elimination after IV and oral dosing respectively. After IV administration, distribution was rapid (T(1/2(d)) 0.23+/-0.24 h) and wide, as reflected by the steady-state volume of distribution of 1.01+/-0.15 L/kg. Elimination from the body was slow with a body clearance of 0.09+/-0.02 L/h kg and a T(1/2) of 7.98+/-0.57 h. After repeat oral administration, absorption half-life was 0.86+/-1.59 h and T(max) of 1.94+/-2.11 h. Bioavailability was almost complete (99+/-29%) with a peak plasma concentration at the steady-state of 1.97+/-0.61 mug/mL. Drug accumulation was not significant after six oral administrations. Calculation of efficacy predictors showed that marbofloxacin has good therapeutic profile against Gram-negative and Gram-positive bacteria with a MIC(50) value <0.25 microg/mL.