The purpose of this research paper is to describe the characteristics and electrochemical performances of a pressurized alkaline water electrolysis short stack (5-cells, 0.5 kW) operated at 80 degrees C, from atmospheric pressure up to 100 bars. Expanded grids of metallic nickel covered with specific porous catalytic structures have been used as working electrodes. A polysulfone-based diaphragm with a high ionic conductivity has been specifically designed for operation in pressurized alkaline water electrolysis cells. I-V polarization curves have been recorded at current densities up to 1000 mA/cm(2), at temperatures up to 80 degrees C and under pressures up to 100 bars. The water electrolysis efficiency of this short-stack has been determined. A specific energy consumption of ca. 4.4-4.5 kWh/Nm(3) has been obtained in the high current density range. Durability tests have been performed on the short stack over 1000 h. A limited degradation rate <5 mu V/h has been recorded over that period of test. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.