Formative assessment measures are commonly used in schools to assess reading and to design instruction accordingly. The purpose of this research was to investigate the incremental and concurrent validity of formative assessment measures of reading comprehension. It was hypothesized that formative measures of reading comprehension would contribute more to our understanding of students' overall reading abilities than simply oral reading fluency (ORF). It was also hypothesized that measures could be modeled in a meaningful way to explain student performance on criterion measures of academic competence. Four formative measures of reading comprehension--maze (MZ), retell fluency (RTF), written retell (WRT), and sentence verification technique (SVT)--were used to measure unique aspects of reading comprehension through production-type responses. Results suggested that reading comprehension measures, when combined with ORF, added to the total variance associated with reading ability and were reliable indicators of student performance on a high stakes criterion-referenced assessment of grade-level literacy. (Contains 4 tables.)