OBJECTIVE To determine whether the Touch Window or the mouse with an enlarged on-screen arrow was more effective or efficient for an on-screen letter-matching task completed by a boy 9 years of age with spastic quadriplegic cerebral palsy and visual and cognitive deficits. METHODS A single-subject research design of 5 treatment phases, A1, B1, A2, B2, and A & B, was used. The total percentage of correct letter matches per treatment session, the total percentage correct per letter, and the amount of time needed to match 5 consecutive letters correctly were evaluated. RESULTS The range and variability of letters correctly matched per session decreased and trends for correct letter matches accelerated when the participant used the mouse interface. Accuracy with matching 18 of 26 (69%) letters of the alphabet increased when selections were made with the mouse interface. The participant was faster when using the Touch Window to match 5 consecutive letters correctly; however, regardless of the interface device used, letter matching remained slow and tedious. CONCLUSIONS The mouse with an enlarged on-screen arrow and cursor was the more effective interface device with this child. Making a minor adjustment such as increasing the size of the on-screen arrow can make a common piece of equipment accessible to a person with disabilities.