The U.S. Air Force has a continuing interest in reducing high rates of attrition and training-block failures (known as washbacks, in which portions of training must be repeated) during initial skills training. High attrition requires a significantly greater input into the schoolhouses, increasing training and recruiting costs. High washback rates reduce the capacity of the schoolhouses by requiring that seats be set aside for students who need to retake training blocks, and such rates incur greater costs by increasing training time. The U.S. Air Force (USAF) Directorate of Force Management Policy (AF/A1P) tasked the RAND Corporation to investigate enlisted USAF specialties with high attrition and washback rates. The research described in this report extended over two years, divided into two phases. The first phase was the investigation of five career fields defined by the following Air Force specialty codes (AFSCs): 1C1X1, air traffic control (ATC); 1C2X1, combat control (CCT); 1T2X1, pararescue (PJ); 2A6X2, aerospace ground equipment (AGE); and 3E8X1, explosive ordnance disposal (EOD). This research was conducted as part of a fiscal year (FY) 2008 umbrella study called Enhanced Testing and Screening for High Value and High Attrition Programs. The second phase continued the investigation into four other career fields: AFSCs 1N0X1, operations intelligence; 1N4X1, network intelligence analysis; 1N3X4X, Far East linguist; and 1N3X5X, Middle East linguist. This research was conducted as part of an FY 2009 umbrella study, Personnel Selection and Screening. Over the course of the research, RAND researchers briefed numerous senior decisionmakers on its findings. Consequently, many of the recommendations have been or are in the process of being implemented. The report credits the Air Force for changes made through 2010 but does not include changes made after 2010.