Abstract: An intake system for a rotary piston engine having a plurality of engine sections, each engine section being separated by an intermediate housing. In the intake system, there are provided communicating passages for communicating the engine sections so that intake air can be transferred between working chambers formed in the engine sections in accordance with a difference in rotor phase between the engine sections. The communicating passage is located so as to be closed after an intake port is closed in each engine section and positioned so that there remains a larger amount of intake air in each of the working chambers than the minimum amount of intake air required for ensuring idling rotation speed under idling engine operating condition when the communicating passage is closed. This intake system makes it possible to obtain a rotary piston engine which can remarkably reduce pumping loss and desirably control the amount of intake air in accordance with an engine operating condition.