This investigation examined the effects of currently available word prediction software programs that support phonetic/inventive spelling on the quality of journal writing by six students with severe writing and/or spelling difficulties in grades three through six during a month-long summer writing program. A changing conditions single-subject research design was used and replicated across the participants. Using a daily writing prompt, students alternated between "Co:Writer," "WordQ," and "WriteAssist" word prediction programs. The results provided evidence for the effectiveness of various word prediction programs over word processing, and demonstrated improvements in spelling accuracy across conditions. Relative gains in the total number of words and composition rate were modest for the majority of the participants and should be interpreted with caution due to several methodological issues. The social validity interviews revealed that all students enjoyed the word prediction programs and found them beneficial. Study limitations and recommendations for future research are discussed. (Contains 3 figures and 2 tables.)