This study examined the impact of a word prediction software program, Co:Writer, on the written output of 24 students with physical disabilities that affected their ability to write by hand. Surveys were completed by both students who used Co:Writer and their teachers/adult supporters in schools, and 10-minute writing samples were obtained from students in three modalities: handwriting, word processing, and word processing with Co:Writer. Two-thirds or more of the students and 50% or more of the adults believed that Co:Writer helped the students to spell better; use a wider variety of words; write faster; produce neater, easier-to-read work; and write more correct sentences. Further, two-thirds or more of the adults and 50% or more of the students believed that Co:Writer helped the students to write more without tiring, experience less frustration when writing, and read what they had written. The writing sample analyses indicated no significant difference between the three writing modes with regard to the total number of words produced in 10 minutes. However, word processing and/or Co:Writer resulted in higher percentages of legible words, correctly spelled words, and correct word sequences; and in longer mean lengths of consecutive correct word sequences than handwriting. The results are discussed in terms of their relevance to educational technology supports for students with physical disabilities. (Contains 3 tables and 4 footnotes.)