Abstract: A rotary internal combustion engine comprising at least one but preferably a plurality of two operating chambers each having a toroidal path of travel on an interior thereof and an interactive piston assembly comprising a pair of first or driven pistons connected to a power take-off and a pair of second or driving pistons concurrently movable along the toroidal path of travel relative to said pair of first pistons. In each chamber, the pair of second pistons is periodically positionable, during each revolution, in driving relation to the pair of first pistons and is cooperatively structured therewith to accomplish the various phases of an engine cycle during forced travel of the pair of first pistons along the toroidal path of travel, thereby causing forced rotation or driving of the power take-off.