Regular physical activity participation throughout childhood provides benefits to physical (Malina, Bouchard, & Bar-Or, 2004), physiological (Andersen, Wedderkopp, Hansen, Cooper, & Froberg, 2003), and psychological health (Mutrie & Parfitt, 1998). In recognition of these benefits, guidelines have been published in the United States (Corbin & Pangrazi, 2003) and United Kingdom (Biddle, Sallis, & Cavill, 1998) recommending that children should accumulate at least 60 minutes per day of moderate-to-vigorous physical activity (MVPA). Though there is evidence to suggest that this target is being attained (Pate et al., 2002; Sleap & Tolfrey, 2001; Sproston & Primatesta, 2003), reviews of children's physical activity have concluded that at least 50% of young people are insufficiently active at a level to confer health benefits (Armstrong & Van Mechelen, 1998; Stone, McKenzie, Welk, & Booth, 1998). The purpose of this paper was to review the literature describing physical activity levels during elementary school physical education classes. The time that the students spent in MVPA was the main outcome variable, which was analyzed in relation to measurement instrument, student grade level and gender, type of physical education activities, and intervention treatments. A total of 44 papers were reviewed. (Contains 2 tables and 1 figure.)