Extremely slow communication is a daily reality for many people with different forms of physical disability. Modern computer interfaces can be designed to enhance expressive communication. This is accomplished first by supplying facilities to tailor them to each particular user's residual physical disabilities, and second by automatically supplying much of the redundancy inherent in natural communication. In the first part of this book a functional architecture for communication aids is discussed and the idea of automatically supplying the intrinsic redundancy contained in natural communication is explained. The distinctions between adaptive and non-adaptive models of communication are shown and details are given of working predictive text generation systems. One such system is the Reactive Keyboard, and in the second part of the book this is described. It greatly speeds communication by predicting the user's next response before it is made, although it does not always predict correctly. The guesses are made on the basis of previous answers and thus can conform to whatever kind of text is entered. Versions of the Reactive Keyboard exist for Unix, IBM PC, and Macintosh systems, free of charge, and can be tailored to individual user needs. This book will be of great value to all involved in helping disabled users interact with computers.