This article describes an automated patient registration/treatment randomization system for multicenter clinical trials. Registrations take place centrally using telephone keypads (tone-dial) for data entry and synthesized speech (at the coordinating center) for confirmation. The system permits a wide variety of protocol designs and treatment assignment schemes and presently supports more than 85 protocols of the Pediatric Oncology Group. It is developed in modules to permit easy addition/deletion of studies and treating sites. The system permits uninterrupted, unattended operation at the coordinating center 7 days a week, 24 hours a day.