Potentially, physical education provides the greatest opportunity to impact the largest number of children in the fight against obesity through physical activity (PA). Therefore, it is necessary to systematically determine what occurs during physical education instruction as it relates to such factors as lesson context, teaching behaviors, and middle school students' levels of physical activity. The purpose of this study was to examine children's levels of physical activity specific to lesson contexts and teaching behaviors naturally occurring during middle school physical education instruction. A case study design examined a single, rural middle school physical education program, located in the Southeastern region of the U.S. Study participants included all physical education teachers (N = 4), one intern, and two-thirds of all middle school students (N = 207; 106 females and 101 males), grades 6-8. IRB approval and informed consent of all participants were obtained. Researchers observed three middle school physical education classes twice weekly across most of one academic year, using the System for Observing Fitness Instruction Time (McKenzie, 1999; SOFIT) to collect data on lesson context, teaching behaviors, and levels of physical activity. Four students per physical education lesson were observed on a rotating basis, adhering to SOFIT protocol while using a 20-second observation interval. Percent time spent in lesson contexts was 25.57% (management), 23.02% (PE general knowledge instruction), 3.27% (physical fitness knowledge instruction), 19.50% (fitness-related activity), 7.04% (skill practice), 20.35% (game play) and 1.25% (free play). Percent time spent in specified teacher behaviors was 1.00% (promotes fitness), 4.4% (demonstrates fitness), 46.9% (instructs generally), 26.7% (manages), 15.9% (observes), and 5.1% (other task). Descriptive statistics revealed mean levels of PA (1-lying down to 5-very active) under these lesson contexts: management (2.80), PE general knowledge instruction (2.28), physical fitness knowledge instruction (2.57), fitness-related activity (3.90), skill practice (3.61), game play (3.36), and free play (1.95). Mean levels of PA associated with specific teaching behaviors were promotes fitness (4.77), demonstrates fitness (3.83), instructs generally (2.83), manages (2.89), observes (3.55), and other task (3.31). Highest levels of PA during physical education instruction occurred during activity-type lesson contexts as expected. Interestingly, the lowest level of PA occurred during the free-play lesson context. Perhaps structured activity lesson contexts provide a more appropriate level of PA than unstructured activity lesson contexts. Highest levels of PA occurred when teachers were either promoting fitness or demonstrating fitness, or observing as expected. Results provide a springboard for comparable large-scale investigations.Keyword(s): health promotion, middle school issues, physical activity