A book which summarizes many of the recent advances in the theory and practice of achievement testing, in the light of technological developments, and developments in psychometric and psychological theory. It provides an introduction to the two major psychometric models, item response theory and generalizability theory, and assesses their strengths for different applications. The book closes with some speculations about the future of achievement tests for the assessment of individuals, as well as monitoring of educational progress. `...the book contains valuable information for both beginners and for advanced workers who want an overview of recent work in achievement testing.' -- The Journal of the American Statistical Association, June 1985