Abstract: A catalytic combustion engine, each cylinder of which has a pre-combustion chamber communicating through an inclined transfer cylinder to produce swirl around the chamber, and has a pair of spaced parallel or nearly-parallel catalytic screen elements, e.g. gauzes, mounted to both the mouth of the transfer passage and the fuel injector nozzle, so as to be clear of the circumferential swirl path of the gas circulating in the chamber. The minimum spacing between the two catalytic screens should exceed the width of the mouth of the transfer passage. The injector injects a fuel spray between the two catalytic screens which preferably just brushes each screen and impinges on a heater plug. The compression ratio may be much lower than that for a conventional Diesel engine, for example down to 12:1.