The chapter discusses the process of decimation and interpolation in a signal processing system. Implementation is done using a finite impulse response (FIR) filter, which allows reducing and increasing the sample rate. The frequency domain view of decimation and interpolation is explained. It also discusses situations of high oversampling of a signal, resampling of noninteger value, and the interpolation effects. It concludes with explanation of resampling by a noninteger rate.