Abstract: A conversation channel allocation method is provided for a mobile communication system of MCA method to perform allocation of conversation channels between base stations and mobile stations. At a congestion state where all of the conversation channels are used for conversations respectively, when a new conversation request is given from a mobile station, a control channel, which is originally used for transmission of a control signal, is allocated to such a mobile station as a new conversation channel. Thus, the mobile station is capable of performing radio communication with the base station by using the control channel, so that a calling party is capable of performing conversation with a called party without interruption. When the conversation completes, the control channel is restored by canceling its function as the new conversation channel.