We have developed a prototype communication system which helps non-speakers to perform communication acts competently, rather than concentrating on improving the production efficiency for specific letters, words or phrases. The system, called CHAT, is based on patterns which are found in normal unconstrained dialogue. It contains information about the present conversational move, the next likely move, the person being addressed, and the mood of the interaction. The system can move automatically through a dialogue, or can offer the user a selection of conversational moves on the basis of single keystrokes. The increased communication speed which is thus offered can significantly improve both the flow of the conversation and the disabled person's control of the dialogue.