We have revisited hydrogen behavior in Fe-Ni alloys with the tritium evolution technique. Applying a 3D analytical solution of Fick's diffusion equation to the tritium evolution curve from disk shaped samples, hydrogen retention and apparent diffusion coefficients in Fe-Ni alloys with Ni content from 6 to 50 at.% are determined around RT. In gamma phase region, diffusion coefficients were not appreciably changed and increased with lattice parameter. In the alpha' phase region, two diffusion components were distinguished: For fast diffusion components, diffusion coefficients have quite good agreement with the literature value and decreased with increase of lattice parameter. The slower diffusion components are likely attributable to retained gamma phase precipitates or Ni(3)Fe dispersed in the alpha' matrix and must be very important to understand hydrogen embrittlement and tritium safety handling. (C) 2008 Elsevier B.V. All rights reserved.