Beginning in the early 1980s and continuing through the middle 1990s, the U.S. Army Research Institute for the Behavioral and Social Sciences (ARI) sponsored a comprehensive research and development program to evaluate and enhance the Army's personnel selection and classification procedures. This was a set of interrelated efforts, collectively known as Project A. Project A had a number of basic and applied research objectives pertaining to selection and classification decision making. It focused on the entire selection and classification system for Army enlisted personnel and addressed research questions that can be generalized to other personnel systems. It involved the development and evaluation of a comprehensive array of predictor and criterion measures using samples of tens of thousands of individuals in a broad range of jobs. The research included a longitudinal sample--from which data were collected at organizational entry--following training, after 1-2 years on the job and after 3-4 years on the job. This book provides a concise and readable description of the entire Project A research program. The editors share the problems, strategies, experiences, findings, lessons learned, and some of the excitement that resulted from conducting the type of project that comes along once in a lifetime for an industrial/organizational psychologist. This book is of interest to industrial/organizational psychologists, including experienced researchers, consultants, graduate students, and anyone interested in personnel selection and classification research.