Despite the U.S. Army Junior Reserve Officers' Training Corps' (AJROTC's) longevity, the scope of its reach, and the size of its budget, little is known about the associations between AJROTC participation and outcomes of importance to the country and military. To understand these effects, the authors reviewed U.S. Department of Defense, Army, and U.S. Army Cadet Command policies and regulations and created a logic model to identify desired outcomes. They conducted interviews with Junior Reserve Officers' Training Corps (JROTC) and school stakeholders to determine important program characteristics, such as student experience, how the value of the program is communicated and perceived, and how program modernization efforts (including science, technology, engineering, and mathematics [STEM]-focused efforts) align with the curriculum. Using individual-level data on programs in Texas and Hawaii, the authors analyzed participant outcomes both in high school and beyond, with a focus on STEM-related outcomes. The authors found that AJROTC serves more-economically disadvantaged schools and students, which makes simple benchmarks less informative. Once accounting for these differences, the authors found that cadets who participate in all four years of AJROTC are more likely to graduate, have higher rates of attendance, and have lower rates of suspension compared with matched peers. However, after graduating from high school, they are less likely to immediately enroll in college and more likely to plan to join the military. Former JROTC (any service) cadets who enlist in the Army are more likely to complete their first terms and more likely to pursue STEM occupational specialties.