The kinetics of absorption, distribution and elimination of ciprofloxacin and fleroxacin (following an intravenous dose of 200 mg), were evaluated in 24 adult healthy male Nigerian volunteers. Appropriate mathematical models were applied with the aid of a microcomputer software program for the estimation of the basic pharmacokinetic parameters. Appropriate statistical tests and profiles formed the basis for accepting or rejecting a proposed model. For parametric comparisons between the profile of the two drugs, the null hypothesis of no difference in their pharmacokinetic profile was proposed. All statistical tests were performed at a significance level of 95% (alpha = 0.05) and the 95% confidence level was determined where appropriate. Additionally, the model-independent or stochastic method of analysis was also employed in the pharmacokinetic evaluation of the blood level data. The parametric estimates obtained from both methods were compared. The plasma elimination half-life (t1/2) was estimated as 13.8 +/- 5.5 h for fleroxacin and 7.5 +/- 4.0 h for ciprofloxacin; the maximal plasma concentration (Cmax) was 0.8 +/- 0.3 and 2.3 +/- 1.0 mg/l for fleroxacin and ciprofloxacin, respectively, whilst the volume of distribution (Vd) was 2.5 +/- 1.6 and 0.4 +/- 0.3 liters/kg for fleroxacin and ciprofloxacin, respectively. 71 and 70% of unchanged drug were excreted in urine for fleroxacin and ciprofloxacin, respectively. With respect to comparative values, the results confirmed trends already observed in the literature, particularly as regards the t1/2. However, for fleroxacin there was a significant deviation from the literature trends with respect to Vd, Cmax and AUC. The results also confirmed earlier findings, advocating a once-daily dosage schedule for fleroxacin also in the Negroid population.