Abstract: In a rotary internal combustion engine the cylinders forming the combustion chambers are circumferentially arranged in a rotatably mounted engine housing. The housing is fixed to the engine shaft which in turn is journalled for rotation in a supporting framework. A brake mechanism is provided for holding the pistons with respect to the supporting framework during a power stroke preventing retrograde movement of the pistons to thereby urge the housing and shaft to rotate. Upon cessation of the power stroke, the brake is released, the pistons rotate with the housing and a bias spring assembly is provided to urge the pistons into the cylinder in a compression stroke. The engine thus is continuously rotated to deliver power output at the shaft.