Career academies, after more than four decades of development and three decades of evaluation, have been found by a conclusive random assignment study to be effective in improving outcomes for students during and after high school. Career academies have therefore become the most durable and best-tested component of a high school reform strategy to prepare students for both college and careers. The number of career academies has been expanding rapidly, in part because academies have been found to be effective, and in part because they embody ideas promoted by several major high school reform movements. This paper describes the growth and evolution of career academies, reviews the evaluation evidence, explains how career academies reflect widely accepted principles of high school reform, and considers prospects for the future. (Contains 5 tables, 1 figure and 10 footnotes.) [Originally prepared as an update and condensation in 2000 of the book: "Career Academies: Partnerships for Reconstructing American High Schools" (ED361409) published in 1992, this document brings up to date the history and research findings regarding career academies.]