Proton conducting membranes have been prepared from chloro-sulfonated polyetheretherketone with cardo group polymers at various sulfonation degree via casting solutions using dimethylformamide as a solvent. The proton conductivity of sulfonated polyetheretherketone with cardo group membranes has been evaluated in the temperature range between 80 and 120 degrees C and the best result of this work has been achieved at 120 degrees C and sulfonation degree equal to 60% with a value equal to 6.7.10(-2) S/cm. Furthermore, this sample shows an open circuit voltage varying from 0.881 V at 80 degrees C to 0.867 V at 120 degrees C, pointing out that the membrane performance is not greatly affected by a temperature variation. Nevertheless, an increase of temperature from 80 to 120 degrees C makes possible an increase of the cell resistance varying from 0.17 to 0.24 Omega cm(2). Thus, the present study investigates the performance of sulfonated polyetheretherketone with cardo group membranes in terms of polarization curves, open circuit voltage, cell resistance and proton conductivity in order to propose them for proton exchange membrane fuel cell applications, particularly at T > 100 degrees C. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.