In this report, the development, field testing, and validation of the Classroom Literacy Environment Profile (CLEP) are described. In the first phase, characteristics of print-rich classroom environments were identified, defined, and organized into categories through a review of the literature, classroom observations, and teacher focus groups. In the second phase of the project, categories and themes interpreted from phase one data were used to write and review the initial items of the instrument. In phase three, generalizability evidence for the CLEP instrument was examined using a G or generalizability study. Classrooms and items evidenced large variance components indicating that the degree of implementation of print-rich classroom environments was reliably discriminated using the CLEP. Following the G study, three D or decision studies were conducted in which the numbers of raters and the number of rating occasions were varied to determine acceptable levels of generalizability and error.