In 1998, President Clinton signed the federal Workforce Investment Act (WIA). Implemented in 2000, WIA replaced the Job Partnership Training Act (JTPA) as the primary federal job training program. Congress viewed WIA as a way to end "business as usual" in the workforce investment system. WIA aimed to transform the employment and training system by streamlining service delivery and providing universal access to services. It promoted customer choice by giving state and local agencies more flexibility in service design, attempted to more fully engage businesses, and fundamentally changed the service provided to youth. WIA was scheduled for reauthorization in 2003, but another eight years have passed without congressional action. During this time, WIA has continued to evolve. In this article, the authors aim to synthesize what they know empirically about the WIA program and discuss lessons for WIA reauthorization. In particular, they explore the design of the WIA program and its initial implementation and evolution. They also examine the extent to which states and local areas have taken advantage of the flexibility inherent in WIA's design. Since results from an experimental evaluation of WIA will not be available until 2015, they present evidence from evaluations of prior federal job training programs as well as nonexperimental evaluations of WIA and experimental evaluations of WIA service components. The authors are interested in evidence of the impact of WIA on participants, the impact of WIA service components, and any evidence about the impact of WIA on different populations of workers. (Contains 1 figure, 2 tables, and 9 footnotes.)