Although limited research exists on the appropriateness of Advanced Placement (AP) and International Baccalaureate (IB) Programs for gifted secondary learners, these courses serve as the primary methods of meeting the needs of gifted students in most high schools. This qualitative study employed a grounded theory approach to investigate how teachers conceptualize and implement curriculum and instruction in AP and IB courses and how students enrolled in AP and IB classes perceive and evaluate their learning experiences in these environments. Interviews with and observations of 200 teachers and 300 students in 23 high schools revealed that the end-of-course AP and IB exams drove most teachers' curricular and instructional decisions. Most AP and IB teachers also perceived the students in their courses as a homogeneous group of successful, self-motivated, and driven students. Accordingly, the curriculum and instruction within AP and IB courses was largely one-size-fits-all and fast-paced. Most AP and IB students perceived these courses to be the most challenging and satisfying of any courses they had taken, and described them as a welcome "escape" from general education and even honors courses. However, some students, including students from traditionally underrepresented populations and students who did not fit the "AP/IB mold" of long-time school success--did not perceive the one-size-fits-all, fast-paced courses to be a good fit for their needs. Many AP and IB students also noted that the very heavy workload in these courses left them little time for sleep or other activities; however, most students believed that the benefits they would accrue from completing these courses, such as admission to elite colleges and universities and earning college credits, was worth the hard work. Implications of these findings and recommendations for increasing the goodness of fit of AP and IB courses for--and consequently increasing the participation of--students from a wide variety of backgrounds are discussed. Eight appendixes are included: (1) Demographics by School; (2) Observation Protocol; (3) AP Teacher Interview Questions; (4) IB Teacher Interview Questions; (5) AP Student Interview Questions; (6) IB Student Interview Questions; (7) Former AP Student Interview Questions; and (8) Former IB Student Interview Questions. (Contains 1 table and 3 figures.)