A study was conducted of the feasibility of establishing an equivalency scale that would enable commercial state tests to be linked to one another and to the National Assessment of Educational Progress (NAEP). In evaluating the feasibility of linkages, the study committee focused on the linkage of various fourth-grade reading tests and the linkage of various eighth-grade mathematics tests. Committee members concentrated on the factors that affect the validity of the inferences about student performance that users would draw from the linked test scores. The committee concluded that comparing the full array of currently administered commercial and state achievement tests to one another, through the development of a single equivalency or linking scale, is not feasible. Nor is reporting individual student scores from the full array of tests on the NAEP scale and transforming individual scores on these tests and assessments into NAEP achievement levels feasible. Under limited conditions, it may be possible to calculate a linkage between two tests, but multiple factors affect the validity of the inferences drawn from the linked scores. Unless the test to be linked to the NAEP is very similar in content, format, and uses, the resulting linkage is likely to be unstable and potentially misleading. (Contains 3 tables, 3 figures, and 81 references.) (SLD)