Reported are the results and conclusions of an arithmetic investigation made in the schools of Scotland in the spring and fall of 1966. The first problem in this investigation was to ascertain which, if either, of two unlike programs of instruction was more effective in developing skill in computation. The second was to determine the value of an unusual design for this kind of evaluative research. The programs in question are the Cuisenaire (Cui.) system of instruction and the Traditional (Tra.) system, both systems defined as they were taught in the school year 1963-65. The subjects for this study were l,l09 Scottish children ranging in age from 91 to 119 months, with a mean age of approximately 100 months. One group of subjects consisted of 539 children who had studied arithmetic according to the Cui. program for three years, in Primary I, II, and III. The second group of 570 children had been taught arithmetic in the same grades according to the Tra. program. From the evidence obtained, it is reasonable to suggest that children identified as low in intelligence and exposed to a relatively long period of instruction in arithmetic will gain more through involvement in the Cui. program. No claims for the superiority of either program can be made with respect to other sub-samples or the total samples selected for this investigation. (RP)