The influences of oxygen pressure on the phase composition, microstructural evolution of the combustion products during combustion synthesis of ZnFe2O4 through iron, iron oxide and zinc oxide powders are discussed. Single spinel-phase zinc ferrite can be obtained when the oxygen pressure is 1.0 MPa and non-stoichiometric oxides, Fe1-xO and Fe1-zO are formed at high or low oxygen pressure. Moreover, an analysis of the dependence of the degree of conversion to ferrite, eta, on oxygen pressure has also been made. For a given porosity and combustion temperature, the degree of conversion increases with the oxygen pressure increasing and for any given porosity and degree of conversion, higher oxygen pressure is required at higher temperature. (C) 2003 Elsevier B.V. All fights reserved.