The purpose of this descriptive component of a larger, exploratory case study was to examine associations among lesson contexts, teacher behaviors, and adolescent physical activity over a year of physical education (PE) at one school. Middle school students (n = 206) and their PE teachers (n = 4) were observed twice-weekly across one academic year. Data were collected using the System for Observing Fitness Instruction Time (SOFIT), Behavioral Evaluation Strategy and Taxonomy (BEST) software and Yamax SW-200 pedometers. Students spent 32.5 percent lesson time in at least moderate intensity activity, averaging 1542 steps per lesson. Higher activity levels were associated with lesson contexts of fitness activity, skill activity, and game play; while lowest activity levels occurred during free play. Higher activity levels were associated with teacher behaviors of promoting fitness, demonstrating fitness, and observing; lower activity levels were associated with teacher behaviors of general instruction and management. (Contains 4 tables.)