The development of technologies to assist people with severe and profound developmental disabilities to engage in constructive activity without constant support from carers may assist such persons to participate fully in vocational and other occupational activities. We describe the development, evaluation and use of VICAID, a system based on a radically simplified palmtop computer. The VICAID system enables a person with a developmental disability to access pictorial instructions designed to help him or her in the accurate completion of tasks. It also provides reminders to access the instructions, and/or alerts a job coach or supervisor should the worker's interaction with the system suggest that they are having difficulty with a task. Evaluative studies show that (1) the system is more effective than alternative supports (pictorial instructions presented in booklets) in maintaining accurate task performance, (2) that the system is preferred to such booklets by most users with severe disabilities, and (3) that it can be used in real work settings. Future development of the system will require attention to be paid to issues of training job-coaches and support workers in its setting-up and maintenance.