The Anchor Test Study provides a method for translating a pupil's score on any one of eight widely used standardized reading tests for Grades 4, 5, and 6 to a corresponding score on any of the other seven tests, as well as furnishing new nationally representative norms for each of the eight tests. In addition, the Study presents new estimates of alternate form reliability for each test, provides estimates of the intercorrelations among the tests, and explores empirically some methodological questions in test-equating. The major purpose of the Anchor Test Study Supplement is to equate the Gates MacGinitie Reading Test (1964) to the other seven tests in the Study: California Achievement Tests (1970), Comprehensive Tests of Basic Skills (1968), Iowa Test of Basic Skills (1971), Metropolitan Achievement Tests (1970), Sequential Tests of Educational Progress (1969), SRA Achievement Series (1971), and Stanford Achievement Tests (1964). This volume of the Supplement includes information on administration and processing, design of the sample, methodology, and results. Some materials originally included in this volume were eliminated due to copyright restrictions. (RC)