Abstract: A rotary piston engine, comprising at least two working chambers formed by a housing, a working rotary piston rotating therein and at least one rotating auxiliary rotary piston. A method of operating the rotary piston engine. In order to allow different compression ratios and ignition timings and in order to increase the rotatability and leakproofness of the rotary pistons even during long-term operation of the rotary piston engine of the type in question, the rotary piston engine comprises at least two working chambers, which are formed by a housing, a working rotary piston rotating therein and at least one rotating auxiliary rotary piston, wherein a working gas can be transferred via at least one duct from at least one of the working chambers into at least one other of the working chambers.