Acoustic bottom reverberation from a water–sediment interface for bistatic source and receiver configurations in range-dependent, multi-layered, shallow-water environments is calculated with a normal-mode model. The signal field is propagated to and from the scattering regions using adiabatic normal-mode theory. Scattering from the ocean bottom is treated using a three-dimensional Lambert’s-law/facet reflection model. An explicit descripion of the coupling between incident and scattered modes and their contribution to reverberation is obtained. When all possible contributions are considered, the computation time is proportional to the product of the number of incident modes and the number of scattered modes. If the modal contributions to reverberation are weighted and sorted into nonincreasing sequences, then the subsequent summation over all modes may be truncated at a desired level of accuracy. A dramatic increase in computational efficiency may be achieved. Results for a realistic ocean environment are presented which illustrate some of the features of the model. [Work supported by Office of Naval Technology, Code 234.]