In this paper we will define and study what we call "cellular" multiuser communication systems (MCSs). These systems can be thought of as models for cellular telephone systems using FDMA or TDMA multiaccess protocols. A cellular MCS is characterized by a set of TV cells, and a set of n channels. Within each cell, a certain number of two-way conversations ("calls") may take place, with each call occupying a distinct channel. In certain circumstances a given channel may be used simultaneously in several different cells. This permissible channel reuse is described by a collection of subsets of cells, called the "maximal reuse sets," the idea being that a given channel may be used simultaneously in each cell of any maximal reuse set.