The paper develops a model for a closed-loop digital control system that incorporates multirate sampling with dynamic compensation. The model completely represents system behaviour at a base sampling rate and at the integral multiple sampling rates in the system. A key feature of the model is that sampling rates can be modified conveniently, without significantly changing the structure of the model. Based on the multirate closed-loop system model, frequency-domain transfer characteristics of the system are developed. These functions are presented in such a way that the performance of different sampling regimes can be compared directly. The eigenvalues of the closed-loop system are also defined so that effects of sampling rate variation may be investigated. An example is included to illustrate use of the model