This paper reports the variation of the pharmacokinetic parameters of ciprofloxacin (CIP) following oral administration of three single doses (10, 20 and 40 mg/kg body weight (b.w.)) to dogs. Plasma and urine samples were assayed by HPLC. The plasma vs. time data were submitted to classical compartmental kinetic analysis (one-compartment open model with a lag time) and to non-compartmental data analysis. The maximal plasma concentrations attained after administration of 10 and 20 mg/kg were 1.55 and 3.08 mg/l, respectively, and agree with results reported in the literature for this species. The absorption was slower and showed a longer and more variable lag time when the dose increased. The elimination rate was significantly smaller after administration of the 40 mg/kg (0.0014/min) than 10 and 20 mg/kg doses (near 0.0024/min). AUC/D also showed significant differences. The non-linearity of CIP pharmacokinetics after oral administration was demonstrated by fitting the data AUC vs. dose to a quadratic equation.