This paper proposes multirate signal processing methods for realizing Gaussian scale-space filtering. We introduce new computationally efficient interpolated Gaussian scale-space filters. Also, the use of decimators together with interpolated Gaussian filters is considered. The proposed filtering methods require dramatically less computation than conventional Gaussian scale-space filtering especially in cases where the scale changes with an integer factor. The new filters are extremely efficient when the change in scale is an integer power of two. However, also more complex scaling factors such as y/2 can be efficiently realized.