Abstract: An internal combustion engine comprising a substantially cylindrical casing, a multilobed rotor mounted to rotatably move within said casing, a plurality of substantially cross-sectionally U-shaped combustion chambers slidably mounted in slots or grooves in the casing and projecting inwardly so that the innermost point or face of the chambers are adjacent with the outer face profile of the rotor, the outer profile of said rotor having a circumferential toothed formation thereon, each of said chambers rotatably supporting a gear wheel engaging said toothed formation, ignition means and fuel inlet and exhaust means being provided within the casing for each of the U-shaped chambers, the central longitudinal axis of each combustion chamber being angularly displaced from the radial axis of said casing such that the innermost end of said combustion chamber is displaced in the direction of rotation of said rotor.