This paper presents the experimental results of thallium (III) extraction from NaCl/H2SO4 solution with butyl acetate in hollow-fiber membrane contactors. The experiments were performed using laboratory made modules consisting of hydrophobic polypropylene or polyvinylidene fluoride fibers of different effective membrane areas. The aqueous phase was recirculated between the module and a mixed reservoir, and the organic phase was fed at the shell side in once-through mode. The influences of the aqueous and organic phase flow rate on the overall mass transfer coefficient were investigated. The experimental results are discussed in terms of the fraction of Tl(III) removed from the aqueous phase reservoir and the mean Tl(III) flux through the interfacial area. The results can be used for the design of a hollow-fiber contractor based extraction process that can be utilized in production of the radiopharmaceutical (TlCl)-Tl-201.