Equilibrium and kinetic studies have been carried out on the extraction of uranium(VI) from aqueous nitrate medium into tri-phenylphosphine oxide (TPPO). It was found that uranium extraction by TPPO was suitable in toluene as diluent than cyclohexane and chloroform. Kinetic studies were carried out using a single drop column method. Reaction orders were determined with respect to uranium and nitric acid concentrations in the aqueous phase and TPPO concentrations in the organic phase. It was found that the extraction kinetics could be explained in terms of an aqueous phase interfacial reaction accompanied by diffusion through the interface. Sodium hydroxide solution is suitable for stripping uranium from TPPO in toluene. (C) 2004 Elsevier B.V. All rights reserved.