Combustion knock is one of the primary constraints limiting the performance of spark-ignition hydrogen fuelled internal combustion engines (H2-ICE) as it limits the torque output and efficiency, particularly as the equivalence ratio nears stoichiometric operation. Understanding the characteristic of combustion knock in a H2-ICE will provide better techniques for its detection, prevention and control while enabling operation at conditions of improved efficiency. Engine studies examining combustion knock characteristics were conducted with hydrogen and gasoline fuels in a port-injected, spark-ignited, single cylinder cooperative fuel research (CFR) engine. Characterization of the signals at varying levels of combustion knock from cylinder pressure and a block mounted piezoelectric accelerometer were conducted including frequency, signal intensity, and statistical attributes. Further, through the comparisons with gasoline combustion knock, it was found that knock detection techniques used for gasoline engines, can be applied to a H2-ICE with appropriate modifications. This work provides insight for further development in real time knock detection. This would help in improving reliability of hydrogen engines while allowing the engine to be operated closer to combustion knock limits to increase engine performance and reducing possibility of engine damage due to knock. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.