The purpose of this study is to predict human jejunal permeability (Peff) and fraction absorbed in human (%Fa) for a group of antibacterial fluoroquinolones (FQs), by using a biophysical model based on measured Caco-2 permeability. The predicted Peff (in 10-4 cms-1 units) ranged from 0.7 (norfloxacin) to 4.5 (pefloxacin). The calculated %Fa for norfloxacin = 51% (lit. 35%) and for ciprofloxacin = 76% (lit. 81%). Most of the FQs showed calculated %Fa > 90%, and are expected to be well-absorbed. Estimates of Peff can be predicted by the biophysical model. From these values, the human absorption may be calculated. Where absorption comparisons were possible, the agreement was acceptably good.