The three-parameter logistic model discussed was used by CTB/McGraw-Hill in the development of the Comprehensive Tests of Basic Skills, Form U (CTBS/U) and the Test of Cognitive Skills (TCS), published in the fall of 1981. The development, standardization, and scoring of the tests are described, particularly as these procedures were influenced by the use of item response theory (IRT). Aspects of the development of the tests described include: (1) item tryout data collection design; (2) item statistics; (3) item selection criteria and procedures; (4) data collection and analysis design for equating levels of final tests; (5) maximum likelihood scoring procedures for obtaining trait estimates from number-right scores, as well as from item-response vectors; and (6) Bayesian/IRT procedure for obtaining objective mastery scores. The usefulness of the IRT procedures in clarifying test development and standardization is discussed. (Author)