"HINKLEY, T., J. SALMON, A. D. OKELY, D. CRAWFORD, and K. HESKETH. Preschoolers' Physical Activity, Screen Time, and Compliance with Recommendations. Med. Sci. Sports Exerc., Vol. 44, No. 3, pp. 458-465, 2012. Purpose: Little evidence exists about the prevalence of adequate levels of physical activity and of appropriate screen-based entertainment in preschool children. Previous studies have generally relied on small samples. This study investigates how much time preschool children spend being physically active and engaged in screen-based entertainment. The study also reports compliance with the recently released Australian recommendations for physical activity (>= 3 h.d(-1)) and screen entertainment (<= 1 h.d(-1)) and the National Association for Sport and Physical Education physical activity guidelines (>= 2 h.d(-1)) and American Academy of Pediatrics screen-based entertainment recommendations (<= 2 h.d(-1)) in a large sample of preschool children. Methods: Participants were 1004 Melbourne preschool children (mean age = 4.5 yr, range = 3-5 yr) and their families in the Healthy Active Preschool Years study. Physical activity data were collected by accelerometry during an 8-d period. Parents reported their child's television/video/DVD viewing, computer/Internet, and electronic game use during a typical week. A total of 703 (70%) had sufficient accelerometry data, and 935 children (93%) had useable data on time spent in screen-based entertainment. Results: Children spent 16% (approximately 127 min.d(-1)) of their time being physically active. Boys and younger children were more active than were girls and older children, respectively. Children spent an average of 113 min.d(-1) in screen-based entertainment. Virtually no children (<1%) met both the Australian recommendations and 32% met both the National Association for Sport and Physical Education and American Academy of Pediatrics recommendations. Conclusions: The majority of young children are not participating in adequate amounts of physical activity and in excessive amounts of screen-based entertainment. It is likely that physical activity may decline and that screen-based entertainment may increase with age. Compliance with recommendations may be further reduced. Strategies to promote physical activity and reduce screen-based entertainment in young children are required."