Sixty kindergarten and first grade children took part in an intervention program during which they were confronted with problems requiring concrete operational thought. The study was designed to ascertain the influence of an intervention in the development of operational seriation and transitivity in kindergarten and first grade children who initially failed to demonstrate the ability to do seriation and transitivity problems. Seriation of size, presumably a prerequisite operation for transitive size relations, was also studied. The subjects showed significant advancement toward concrete operation on the seriation problems but failed to show significant improvement on the transitivity problems. In addition, subjects who showed understanding of transitive inference also demonstrated success on seriation, but subjects who showed clear understanding of seriation did not demonstrate success on making transitive inference. Results were interpreted in the context of Piaget's equilibration theory (Genetic epistemology. New York: Columbia University Press, 1970).