This paper brings together a variety of item-analysis techniques into a coherent system. The system is based on classical test theory, the theorems that can be derived from the equation, X = T + E. The system extends from techniques for analyzing parts of an item separately to techniques for relating items to total test score, to sub-scores, to external criterion scores, and to test-retest situations. The system is both mathematically simple and basic and may serve to bring test theory and test practice closer together. (Author)