This study was undertaken to determine the effects of Computer Aided Instruction on mathematics performance of pupils at the grade four level in region #5. This focus was due to the trend of poor performances in mathematics at the national grade four assessments for the past five years. The poor academic performance could be attributed to traditional teaching method commonly used by teachers in the area of study. From the literature reviewed for the study, it was found that Computer Aided Instruction is the most appropriate teaching method since it stimulates the development of critical thinking skills and provides opportunity for active learning. Four intact Grade Four classes in two primary schools were used in this study.