A study assessed the impact of word processing on the writing of junior high school students, experienced in working with computers, for a number of tasks, including writing. Subjects, 111 eighth grade students in four communications arts classes at a Canadian middle-class suburban school, who had been using computers for writing for a year and a half, wrote one story on the computer and one story off the computer. The order in which the two writing tasks were presented and whether the subjects wrote first on or off the computer were different for each class to control for potential order effects with these two factors. Drafts and final versions of the students' writing were scored using a holistic/analytic instrument. Results indicated that: (1) the computer-written work was significantly better in overall quality and better on the competency and mechanics subscales of the evaluation instrument; (2) students produced significantly longer pieces of writing on the computer than off; (3) students reported very positive attitudes toward computer-based editing and writing; (4) there were no macrostructural differences in writing across media; and (5) only one surface feature, spelling, was found to be significantly better in the computer-written work. (Five figures and five tables of data are included; 51 references, the attitude questionnaire, a summary of the scale for evaluating narrative writing, verbal directions for teachers, sample student essays, and four tables of data are attached.) (RS)