This manual contains technical information about the ACT® college readiness assessment. The principal purpose of this manual is to document the technical characteristics of the ACT in light of its intended purposes. ACT regularly conducts research as part of the ongoing formative evaluation of its programs. The research is intended to ensure that the programs remain technically sound. The content of this manual responds to requirements of the testing industry as established in the "Code of Professional Responsibilities in Educational Measurement" (NCME Ad Hoc Committee on the Development of a Code of Ethics, 1995), the "Standards for Educational and Psychological Testing" (AERA, APA, & NCME, 1999), and the "Code of Fair Testing Practices in Education" (Joint Committee on Testing Practices, 2004). This manual is divided into six chapters. The chapters include the following information: (1) An overview of the ACT, its history, its philosophical basis, and the population it serves; (2) Detailed description of the ACT tests; (3) Description of ACT's College and Career Readiness Standards and ACT's College Readiness Benchmarks; (4) Technical characteristics, such as norms, scaling, equating, and reliabilities, of the ACT tests; (5) Validity evidence for the most common uses of the ACT tests; and (6) Description of the noncognitive components of the ACT.