The purpose of this study was to examine the reliability and validity of a basal reading series mastery test. Subjects were 47 fifth graders, who were tested on the SRA Reading Achievement Test, the Ginn 720 End-of-level 11 Mastery Test (MT), and the Word Reading Test. A subgroup of 22 children was tested a second time on the MT. Traditional psychometric correlational analyses as well as strategies specifically designed for examining the adequacy of criterion-referenced tests were applied to the data to investigate the following dimensions of the technical adequacy of the MT: (1) consistency of student performance across two administrations of the MT, and (2) criterion-related validity of the MT scores with respect to two other measures of reading proficiency, and criterion-related validity of the MT mastery/nonmastery decisions with respect to pre/post instructional status. Results indicated that the reliability and validity was acceptable for the composite test scores, but variable for the subtests. Implications for the development and use of criterion-referenced tests are discussed. (Author)