This paper describes a two-dimensional model of an oxygen permeable membrane reactor for partial oxidation of methane (POM). The model covers all aspects of major chemical kinetics, heat and mass transfer phenomena in the tubular reactor with oxygen permeation in radial direction through an ion-conducting membrane. The temperature and concentrations of the major species in the membrane tube were calculated. Results showed that the overall performance of the reactor was strongly dependent on the reactor dimensions and operating conditions. A reactor with smaller diameter (D) and greater length-to-diameter ratio (L/D) gives better performance in terms of high methane (CH4) conversion and high hydrogen (H-2) concentration. Under inlet gas temperature of 900 K and space velocity of 15,000 h(-1), the CH4 conversion and dry H-2 concentration can reach 98% and 64%, respectively, in the reactor with diameter D around 10 mm and L/D > 25. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.