Abstract In order to prepare a complex-forming polymer useful as a selective adsorbent, radiation-induced graft polymerization of acrylonitrile onto a fibrous tetrafluoroethylene ethylene copolymer has been studied by using preirradiation method. The resulting grafted fibers were treated with 3% hydroxylamine alcohol-water solution, followed by controlling in alkali solution. The adsorbents containing amidoxime are able to take up transition metal ions from neutral and weakly acidic solutions while not sorbing the ions of alkaline and alkaline earth metals to any significant extent. It was shown that by introducing a small amount of hydrophilic groups to the fiber, it was possible to increase the exchange rate between the external water and the internal water interacted with functional groups in polymer matrix and to induce the diffusion of hydrated metal ions. The efficiency for adsorption of transition metal ions was successfully improved either by adding small amount of hydrophilic part composed of poly(acrylic acid) or by restricting the distribution of amidoxime groups at the fiber surface. A high stability of this adsorbents to various treatments ( alkali treatment at 80° C, contact with seawater for 24 h at 30° C, etc.) was confirmed. It's applicability to the recovery of uranium from seawater is demonstrated by laboratory scale experiments.