This research, conducted for California State Department of Education, is one component of a feasibility study focusing on ways to make the testing process more efficient by application of multi-purpose tests (MPT). MPT are designed, administered and scored to serve more than one purpose and to consolidate and unify testing programs as a partial solution to test proliferation. A content review identifies common skills measured by the California Assessment Program (CAP) and the Stanford Achievement Test. Empirical information was collected about matched CAP and Stanford item performance from a mathematics field test. A core set of multi-purpose items was identified. A validation study of over 1,000 grade 6 students examined the accuracy of the estimates of norm-referenced test information from the multi-purpose item set identified. The general strategy was to estimate Stanford total test and subtest scores in mathematics by applying item response theory techniques to the identified multi-purpose item set. Estimated scores were then compared with total test and subtest scores actually earned by students. The correlations between pairs of estimated and actual scaled scores were large, and scaled root mean square differences were small. Results indicate: (1) some testing programs evaluate common skills, supporting the concept of a consolidated testing system; (2) there is a need for statewide content domains; and (3) using multi-purpose testing methodology is feasible. (PN)