This paper describes the research activity regarding High Pressure PEM Water Electrolysis conducted at the Energetics Department at the Politecnico di Torino (Turin, Italy). In particular, the first phase of the design and assembly of an in-house made prototype is discussed. This activity was started after a detailed theoretical and experimental work carried on a prototype manufactured by Giner Electrochemical Systems. The experience learned suggested that the new activity should aim at a pressure of about 30-45 bar and higher temperatures, because this pressure range is the one which minimises the electrolysis + compression overall power request, while higher temperature allows to work at lower voltages, thus increasing the electrolyser and the overall process efficiency. On this basis, the design of the electrolyser has been performed, and the elements of the electrolyser have been tested as described in the paper. The tests have been performed at different pressure values, and at different operating temperatures: 40 degrees C and 55 degrees C; a wide range of single cell voltage has been observed: at a current density of 1 A/cm(2), it ranges from 2.1, V (T = 55 degrees C, p = 10 bar) to 2.4 V (T = 40 degrees C, p = 70 bar). Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.