The readability level of passages from three subtests of the Iowa Tests of Educational Development (ITED), Forms X-6 and Y-6, were compared with the readability level of passages selected from the Des Moines Resister, Reader's Digest, Time, Newsweek, Saturday Review, and 18 high school textbooks from the fields of social studies, science, and language arts and literature. The three ITED subtests analyzed were Concepts and Reading Materials in the Social Sciences, Background and Reading Materials in the Natural Sciences, and Literary Materials. Four readability formulas were used to determine the readability levels: the Dale-Chall formula, the Flesch formula, Gunning's FOG Index of Readability, and McLaughlin's SMOG Readability Index. Results indicated that the readability levels of the passages in the ITED social studies, science, and literary subtests were comparable to materials which high school students are likely to encounter both in and out of the classroom. (BW)