A lack of research in adult literacy for both native speakers and speakers of English as a second language led to the development of the Test of Affixes in Syntactic Structures (TASS) for use in a pilot study (Dogger, January 1978) in which knowledge of derivational morphology was tested to determine its possible relationship with reading for English as a second language students. Test construction was followed by a thorough verification procedure which is the purpose of this study. In September 1978 the following measures of test strength were established: construct validity, content validity, item difficulty, item discrimination, internal consistency, rational equivalence, and concurrent validity. The degree of relationship between reading proficiency, as demonstrated by subject performance on the Iowa Silent Reading Test, Level III (ISRT,III), and knowledge of derivational affixes, as demonstrated by subject performance on TASS, was also established. Results show that successful performance on the ISRT, III includes reading strategies beyond those required for successful performance on TASS. In other words, mastery of language structures as represented by English orthography is necessary but not sufficient for college-level reading proficiency.