Abstract: A two-cylinder rotary piston internal combustion engine. Two interengaging arcuate piston-cylinder assemblies move in a circular path on an engine plane. The piston of one assembly and the cylinder of the other assembly reciprocate with respect to each other. Two separate, at least partly hollow, rotating, support shafts are rigidly attached to each said piston-cylinder assembly, one on each side of the engine plane and perpendicular to that plane. Each rigidly attached to its piston-cylinder assembly. Two of these support shafts are concentric with a rotary power take-off shaft, while the other two support shafts are concentric with a flywheel shaft on the opposite side of the plane; the flywheel shaft carries a flywheel. A stationary engine casing surrounds the piston-cylinder assemblies and all the support shafts, with the flywheel shaft and power take-off shaft extending out therefrom.