This study compared the reliability and validity of two different measures of reading ability, the Degrees of Reading Power (DRP) and the Iowa Tests of Basic Skills (ITBS) Reading test and the ITBS Vocabulary test. The data consisted of scores of 377 grade 5 and grade 6 students on these tests, along with their assigned reading levels in the Macmillan reading series, and teacher-assigned grades from two grading periods. Intercorrelations, including disattenuated values, were the primary method of data analysis. The differences between the ITBS and DRP on the reliability and validity evidence presented were minor and appeared to be of limited practical significance. (Author)