his investigation represents an attempt at examining the effectiveness and feasibility of instructional computer use in a Victorian primary school. The study involved the development of a computer assisted instruction (CAI) program for the teaching of addition of vulgar fractions. This was tested with 19 Year 5 children at an independent primary school. The children were tested on the topic before and after exposure to the program, and also received a questionnaire on their attitudes and perceptions. The results were analysed by differing mathematical abilities. The program appeared to be only moderately effective. This could have been because of deficiencies in the program and / or the shortage of student exposure. The effectiveness appeared to be greater for students of medium ability.