A review of research literature revealed that some researchers felt that the use of colored rods, such as the Cuisenaire materials, in teaching number work gave perceptual support to many relationships. Experiments conducted over 3 years attempted to test some of these relationships. During each year, experimental classes in grade one were receiving Cuisenaire instruction while control groups were not. Each ensuing year, classes in grade two and then grade three were included in the experiments. The results from standardized tests and teachers' questionnaires led to the following conclusions: (1) children taught with Cuisenaire materials gained facility in manipulating whole numbers and fractions as shown on a Cuisenaire test; (2) Cuisenaire materials were more effective with bright children; (3) children who used Cuisenaire materials for 2 years scored higher than those using them for 1 year, and they in turn scored higher than the control groups; (4) first grade classes benefited more from the materials than second grade class; and (5) teachers and consultants were enthusiastic about the value of the materials. An extensive bibliography is appended. (JS)