- The benefits of physical activity (PA) are well established (USDDHS, 2008). Concern over the high rate of childhood obesity, however, has highlighted the emphasis of PA. Yet, children and adolescents are not obtaining the recommended amount of PA (CDC, 2011). Physical education (PE) has been recognized as an important source in increasing PA for youth (CDC, 2007). However, research has struggled to establish clear understanding about PE's contribution to the overall activity pattern of its students (Morgan, Beighle, & Pangrazi, 2007) as there has been a number of methodological problems with prior research. The purpose of this study was to examine PE's contribution on overall PA behavior of 34 third and fourth grade elementary students (mean age: 9.2; girls n=15) while addressing the limitations of prior studies through employing an accelerometer-based, multi-site research design. In accomplishing this purpose, Aim 1 examined PE's overall percentage contribution to overall PA while Aim 2 focused on investigating whether students compensate for missed PA opportunities on days in which they do not have PE. PA levels of 34 third and fourth graders from two schools were measured by accelerometers over three data collection periods lasting five days each. At least two weeks separated each collection period. Accelerometers captured PA outcome variables of moderate-to-vigorous physical activity (MVPA), counts, and counts per minute (CPM) on PE days, non-PE days and weekend days. In answering Aim 1, descriptive statistics revealed that the average time spent daily in MVPA was 46.15 minutes (SD= 17.28) while PE accounted for 22.7% (SD= 8.5) of overall MVPA. PE also accounted for 15.12% (SD= 3.46) of overall average counts PA. In answering Aim 2, a one-way repeated measures MANCOVA revealed significant differences between type of day (PE, non-PE, and weekend) and PA levels (Wilks' λ=.64, p<.05; partial η² =.37), with gender and class set as covariates. However, follow-up univariate tests only indicated significant differences between MVPA and types of days, F(2, 62) = 3.56, p<.05, partial η² =.10. On average, the participants received 12 and 23 more minutes of MVPA on PE days than on non-PE days and weekend days, respectively (p<.01), suggesting that the students did not compensate for missed PA opportunities on days in which they did not have PE. Overall, PE was a major contributor of overall MVPA and PA (22.7% and 15%.12, respectively) which is substantial given the 30 minute length of PE classes. In addition, children did not make up MVPA on non-PE days or weekends further bolstering PE’s importance in contributing to overall MVPA behavior. Cumulatively, these findings suggest that more PE classes should be added in order to increase overall PA levels instead of being systematically reduced. However, even with PE, students still did not obtain the recommended amount of MVPA, indicating that PE teachers need to do more to promote out of class PA.