In this paper, problems of fault detection in multirate sampled-data (MSD) systems with time delays are studied. The background of our study is the increasing demands for fault detection in complex, distributed process control systems, where the plant, controllers, sensors and actuators are networked by standardized bus systems. The basic idea behand the problem solutions is to derive the parity relations of the MSD system with time delays by taking into account the multirate nature and the multiple time delays. Having introduced two operators, the fault detection problem can be formulated as an optimization problem in the framework of the well-known parity space method. Application and advantages of the approaches proposed in this paper are finally illustrated by simulation examples and by comparison with other indirect design approaches.