Computers have been used effectively to provide support for people with a variety of special needs. One such group is adults with dyslexia. Dyslexia is commonly recognised as a learning disorder characterised by reading, writing and spelling difficulties. It inhibits recognition and processing of graphic symbols, particularly those pertaining to language. Computers are a useful aid for dyslexic adults, especially word processors and their associated spelling tools. However, there are still areas where improvements are needed. Creating an environment, which minimises visual discomfort associated with proof reading and making selections from lists would be of benefit. Furthermore providing the correct type and level of support for spelling, grammar and sentence construction may result in higher standards being achieved. A survey of 250 dyslexic adults established their requirements and enabled the development of a specialist word processing system and associated spelling support tools. The hypothesis, that using a language with enforced structure and rigid constraints has a positive affect for dyslexic adults, was also tested. A support tool, which provided a controlled environment, to assist with sentence construction for dyslexic adults was developed from this. Three environments were created using the word processing system: environment 1 used the basic system with no support, environment 2 provided spelling support suggested by the survey subjects and environment 3 used the sentence constructing tool providing support and control. Using these environments in controlled experiments indicated that although environment 2 achieved high academic standards, environment 3 produced written work to an even higher standard and at the same time, the subjects derived greater satisfaction in using it. This research proves that working in a controlled, rigid environment, where structure is enforced, substantially benefits dyslexic adults performing computer-based writing tasks.