This study examines the correspondence between a representation of subject-matter structure and a representation of the cognitive structure in students as a result of instruction. Eighty-seven eighth-grade students were assigned randomly to experimental and control treatments. The experimental students (N = 43) studied from a programmed text on probability developed by the School Mathematics Study Group (SMSG). The control group (N - 44) studied from a programmed text on factors and prime numbers. Digraphs, graphs and task analysis were used to map out the content structure. A word association test (WA) was used to measure the existing cognitive structure. The WA test, an achievement test and an attitude measure were given before, after and at a delayed post-experiment time. The results indicate that: (1) eighth-grade students were unfamiliar with the concepts of probability; (2) instruction in probability changed subjects' cognitive structure concerning concepts in probability; (3) the experimental group learned a significant portion of the structure of probability as a matter of instruction while the control group learned almost nothing; and (4) this learning of structure was retained until the retention-test time. (JP)