The AVID Best Practices Study assessed the relative efficacy of 11 AVID program essentials; examined schoolwide effects of AVID; and identified necessary research-based changes in AVID program essentials or staff development. AVID is an elective program for students that provides rigorous academic focus and addresses essential aspects in college preparation. Eight California high school AVID programs were selected based on consistent high performance by AVID students and recommendations of AVID regional directors. During two rounds of site visits, researchers interviewed key program staff, school staff, tutors, and students; observed AVID and academic classes; and examined program and student documents. Data were collected on adherence to the program design. Overall, each of the eight programs followed the AVID design very exactly. The report proposes that the current 11 essentials be maintained and three new essentials be added: AVID provides support for students to succeed in higher level mathematics; AVID teachers participate in ongoing, high quality staff development through regional coordinator workshops and the AVID Summer Institute; and the AVID site coordinator must be a seasoned, highly respected, and dedicated senior teacher with specific knowledge and skills. The paper describes the eight schools, focusing on how they incorporate AVID essentials. (SM)