The anodic oxidation of gallium nitride (GaN) in pH-adjusted N-methylacetamide (NMA) solutions has been carried out by a constant current method. Uniform oxide layers are reproducibly grown in an NMA electrolyte with a pH of 8.0, containing 1% H2O, at a current density of 2.0 mA/cm(2). Under optimum conditions, a linear relationship with a slope of 0.67 nm/V, is obtained between the thickness of the GaN layer consumed in the oxide and forming voltage. Electrical carrier concentration and mobility profiles for Si-doped epitaxial GaN layers are examined by successive Hall effect and sheet resistivity measurements combined with an anodic oxide growth stripping process, where anodization is carried out under optimumly defined conditions. (C) 2004 The Electrochemical Society.