This study is the final report of a three year project to find out if the use of Cuisenaire rods in kindergarten, first, and second grades upgrades arithmetic achievement. Both experimental and control schools enrolled children with average ability who came from lower middle class homes. Children in the experimental kindergarten classes were instructed individually in the use of the rods during each of the 3 years. Both the kindergarten experimental group of 30 children and the kindergarten control group of 23 children were given Test 5 (numbers) of the Metropolitan Readiness Test at the end of the second year. Though both groups did well, experimental students performed significantly higher. The first and second grade groups, who had worked with rods the previous year and two years respectively, were given the Metropolitan Upper Primary Test. Of 26 children in the experimental first grade group, 73 percent had arithmetic totals scores above 80 percentile of the national norming group. Of 19 children in the experimental second grade group, 68 percent were above the 80 percentile. The high test scores of all three experimental groups indicate that use of the rods does upgrade arithmetic achievement. (JF)