Abstract: The present state and the development of the multirate digital control systems are reviewed in this paper. According to the relationships of the different sampling periods of the system, the multirate digital control systems can be catalogued as multirate input controller, multirate output controller and generalized multirate sampled-data control system. They correspond to digital systems with generalized holds, with generalized samplers and with periodic time varying controllers, respectively. The characteristics as well as the recent research results are discussed and outlined. The well-known causality condition, puts the structure constraints on the multirate controllers. The design methods to overcome such constraints and different multirate digital control systems are surveyed.