The focus of this presidential address is on the contemporary treatment of reliability and validity in educational assessment. Highlights on reliability are provided under the classical true-score model using tools from latent trait modeling to clarify important assumptions and procedures for reliability estimation. In addition to reliability, indices of measurement precision that provide information about error tolerance are also discussed. Regarding validity, the focus is on moving from the discrete construct-based model of validity, which still seems to dominate education assessment research and practices, to the unified construct-based model of validity. (Contains 1 figure.)