The steady-state oxygen permeation through polycrystalline La2NiO4+delta, synthesized by a citric acid-based technique and sintered at 1350 degrees C, has been measured as a function of oxygen gradient, temperature (850 - 1000 degrees C), and membrane thickness (0.3 - 2.5 mm). In agreement with earlier reports, the La2NiO4+delta membranes show high permeation rates, comparable to those found for the perovskite-related La1-xSrxCo1-yFeyO3-delta materials. The self-diffusion coefficient and the surface exchange coefficient of oxygen are extracted from the data through transport modeling using averaged bulk transport parameters and through numerical analysis based on a one-dimensional finite-element method. The self-diffusion coefficient and surface exchange coefficients show Arrhenius-type behavior with activation energies 40 +/- 20 and 110 +/- 60 kJ/mol, respectively, and agree qualitatively with literature data obtained by O-16(2)/O-18(2) exchange/secondary ion mass spectroscopy analysis at lower temperatures. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.2138679] All rights reserved.