Reading is perhaps the single most prevalent area of underachievement among learning-disabled students. Accurate assessment of reading difficulties is extremely important not only as a part of the process of determining whether some students are learning disabled but also as a way to determine the nature or cause of their reading problems, such information being needed to decide on the instructional program that the student will need to improve his or her reading skills. While standardized tests of reading comprehension presently available are commonly used to provide evidence of the adequacy of student’s comprehension, they are not diagnostic. They tell us how well a student can perform on the given reading task in comparison to his or her peers, but they do not give insight into the sources of or nature of comprehension deficits. It is for the purpose of gathering such information that diagnosticians rely heavily on the informal reading inventory (IRI) (German, Johnson, & Schneider, 1985; Fuchs, Fuchs, & Maxwell, 1988). Whether published or created by individual school systems or teachers, the technical characteristics of these tests are not well documented, and so they may lack validity and reliability; in addition, effective use of the results depends heavily on the diagnostic skill of the examiner or teacher (Johnston, 1984; Jongsma & Jongsma, 1981).