Fluxes and selectivities for competitive alkali metal cation transport across bulk liquid membranes by the lipophilic crown ether carboxylic acid carrier sym-(octyl)dibenzo-16-crown-5-oxyacetic acid have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, o-dichlorobenzene, toluene and p-xylene. The total alkali metal cation and Na+ fluxes, as well as the Na+/K+ and Na+/Li+ transport selectivity ratios, are compared with selected properties of these organic solvents using the Schmidt, Swain, Koppel-Palm and Kamlet-Taft models. The best correlations are obtained for the Na+ flux and the Na+/K+ transport selectivity.