Abstract: A revolving cylinder internal combustion engine in which a rotor carrying a plurality of piston and cylinder assemblies with their axes at right angles to the rotor axis is mounted in an outer body for rotation responsive to reciprocation of the pistons in the cylinders.In order to improve inlet and exhaust gas control inlet and exhaust to the individual cylinders responsive to rotational movement of the rotor is controlled by cams adjustably carried by the body. Circulation of coolant and/or lubricant through the rotor may be assisted by a centrifugal pumping action responsive to rotor rotation.