Background: Physical activity has many benefits for young children's health and overall development, but few studies have investigated how early care and education centers allot time for physical activity, along with measured individual physical activity levels for indoor/outdoor activities during a typical day. Methods: Fifty early care and education centers in central North Carolina participated in 4 full-day observations, and 559 children aged 3-5 years within centers wore accelerometers assessing physical activity during observation days. Observation and physical activity data were linked and analyzed for associations between child activity and type of classroom activity. Results: Children averaged 51 (13) minutes per day of moderate to vigorous physical activity and 99 (18) minutes per day of light physical activity while in child care. Children averaged 6 (10) and 10 (13) minutes per day of observed outdoor and indoor daily teacher-led physical activity, respectively. Outdoor time averaged 67 (49) minutes per day, and physical activity levels were higher during outdoor time than during common indoor activities (center time, circle time, and TV time). Conclusions: Physical activity levels varied between indoor and outdoor class activities. Policy and program-related efforts to increase physical activity in preschoolers should consider these patterns to leverage opportunities to optimize physical activity within early care and education centers. (author abstract)