Various forms of multiplexing, in which information from several sources is systematically combined and transmitted over a single channel, have been described in the literature. Recent advances in communication theory make possible an examination of the case where isolated transmitters share a common channel without synchronization. This case is important in applications where the transmitters are so separated that synchronization cannot be accomplished directly, but where multiplex operation is nevertheless desired. Under these conditions, it is possible to add redundant information at the output of each transmitter and at the receiver to separate the signals in much the same manner as a desired signal is separated from random noise. Some simple systems are discussed, and general observations on the efficiency of asynchronous multiplex systems are presented.