The separation of tetravalent and trivalent lanthanide ions, Cerium (IV) and Neodymiun (III), respectively, from a sulfate solution through a liquid membrane was examined. TOA was used as carrier extractants and dissolved in kerosene. The liquid membrane was supported by hollow fiber microporous. Sodium carbonate was used as stripping solution. Pure tetravalent lanthanide, Cerium (IV) ions were obtained while trivalent, Neodymium (III), ions could not be extracted and stripped due to the different in form of trivalent and tetravalent lanthanide ions in sulfate solution. The transport system was studied as a function of several variables: concentration of sulfuric acid feed solution, concentration of TOA in liquid membrane, concentration of sodium carbonate in stripping solution, and flow rate of feed and stripping solution. The results indicated that the percentage of extraction is highly dependent on the concentration of sulfuric acid the feed solution and the concentration is 0.2 M for the maximum extraction. Percentage of extraction was enhanced when the concentration of TOA was increased. However, when the concentration of TOA was higher than 4% (v/v) the percentage of extraction was not increased because of the viscosity of liquid membrane. The percentage of extraction and stripping further increased when the concentration of sodium carbonate was increased until the sodium carbonate concentration was 1.25 M. The maximum percentage of stripping for Cerium (IV) of 71% and 100% selectivity was obtained. When the flow rate of feed or solution was increased the percentage of both extraction and stripping decreased due to resident time.