This study examined the efficacy of pentop computers on the written expression of three secondary students with mild disabilities. A multiple-probe design was used to establish pentop computers as a potentially effective tool for increasing the quality and quantity of written expression. Each student learned to use the pentop computer and the accompanying writing software. Students were instructed to write essays without using the pentop computer during baseline, and then with it during the intervention phase. When using the pentop computer, students' essay quality scores increased from baseline; during generalization students' scores decreased. Although a few technological problems were encountered, the pentop computer was found to be a valuable tool for students to use in planning and writing essays. (Contains 1 table and 2 figures.)