Under contract to the National Institute of Neurological and Communicative Disorders and Stroke, we developed a system for prescribing augmentative communication devices for motor-impaired, nonvocal people. The system is novel in that it scores devices for their suitability for a client based on assessments that do not involve trial-and-error evaluation of client performance with devices. The “benchmarks” it calculates are designed to be predictive of the overall utility of a device given the client's needs, and of the communication rate the client will achieve with it once it has become completely familiar. The scoring process is performed by a program known as the Tufts-MIT Prescription Guide, which runs on IBM XT-compatible computers. Special-purpose assessment instrumentation has been developed to perform the motor-assessment tasks required by the Guide to estimate expert rate. An exhaustive questionnaire is used to get at the device features and functions that will be useful and preferable to a client. These needs are inferred by the Guide software from answers to questions concerning the client's living circumstances and preferences. Preliminary data show the benchmark scores aligning well with independent measures of expert user satisfaction and communication rate. This article defines the clinical motivation for the work, outlines a general scheme for predictive assessment, presents a brief overview of the Guide, and delineates one aspect of its function in considerable detail as illustration of the general scheme.