BACKGROUND: Preschool children are recommended to spend at least 15 minutes/hour (25% time) in light-to-vigorous physical activity (total physical activity, TPA). Preschool provider practices, such as whether children are put in small group or whole-group activities, are likely to affect children's TPA levels during preschool. The current study characterized the pattern of physical activity across the preschool day, and examined the relationship of location and social arrangement to TPA. METHODS: Fifteen days from 8 preschool classrooms in 2 preschool centers were video-recorded, and children (N = 73, age = 3-6 years, [mean] = 4.36 [plus or minus] 0.85, Boys = 47%) wore accelerometers for the duration of the preschool day. We observed contextual variables of time (ie, morning or afternoon), location (ie, indoor or outdoor), and for a subsample, social arrangement (ie, activity centers, small group, whole group). RESULTS: Across the whole day, children spent 69.5 [plus or minus] 12.4% time sedentary/inactive and 30.5 [plus or minus] 13.5% time in TPA. Children spent a significantly greater percentage of time in TPA outdoors, compared to indoors (t = 10.00, p .001), and while in small groups compared to whole groups (t = 3.35, p = .009). CONCLUSION: Children spent approximately 30% of the preschool day in TPA. Providing more time outdoors and restructuring preschool activities from whole group to small group could increase the amount of TPA that children accumulate during preschool. (author abstract)