BACKGROUND: Individuals with aphasia often experience difficulties in writing. Word processors with a spell checker and a grammar checker can compensate for some of the writing difficulties associated with aphasia. AIMS: To determine if writing difficulties associated with aphasia may be reduced by the use of a computerised writing aid when training patients. METHODS and PROCEDURES: The writing aids used in this study were originally designed specifically for persons with developmental reading and writing difficulties and are based on statistics of frequent misspellings and phonotactic rules. Three participants with aphasia selected one of two offered writing aids. Written production during treatment and evaluation was recorded and analysed by keystroke logging. The study had a single-subject ABA design replicated across three participants. The baseline (A) was established by measuring four dependent variables. During a 9-week intervention phase (B) the dependent variables were measured once a week. A follow-up (A) was done 10 months after the training was finished. The dependent variables were: total number of words in a writing task; proportion of correctly written words; words per minute; proportion of successful edits. The results were analysed both visually and by statistical calculations. OUTCOMES and RESULTS: All participants experienced a positive improvement in their writing ability. Results showed individual differences; after completed training the first participant made more successful edits, the second wrote more words, had a larger proportion of correctly written words, and made more successful edits. The third participant's results did not show any improvement that could be statistically supported. CONCLUSIONS: This study showed that the computerised training facilitated the generating process and made the revision process more efficient for the participants. The results are important in that they indicate possible ways of designing writing treatment. However, they also show the need for careful analyses when evaluating different treatment strategies and in discussing what improved writing ability may be.