Effects of oxygen off-stoichiometry have been investigated on CuFeO2+delta delafossite-type powders prepared by solid state reaction. Materials annealed at different temperatures under air atmosphere were compared. Thermogravimetric analysis coupled with X-ray structural analysis showed that a powdered CuFeO2 can be oxidized up to CuFeO2+delta with delta=0.18. Electrical measurements confirm the existence of oxidized CuFeO2+delta phases. Particular attention is paid to the correlation between oxidation process and phase stabilities in the CuFeO, and copper spinel phase system. (c) 2005 Elsevier B.V. All rights reserved.