School physical education is listed as one of the recommended intervention points with strong empirical support for promoting regular physical activity (PA) levels in youth (CDC, 2001). However, there is substantial variability and a downward trend in the number of minutes allocated to physical education per week across grade levels (Thomas, 2004). Previous research using self-report measures suggest that most PA occurs beyond school. To date, no study has focused on physical education's contribution to the daily total of PA in middle school students using alternative measurement devices (e.g., pedometers). The purpose of this study was to measure the total daily PA levels of middle school students, and the contribution of physical education lessons to that daily total. Student gender and body composition served as mediating variables. Class periods were 46 min. in length. Students did not wear pedometer during dress times (10 min.). Students wore the pedometers sealed for the first five days, and unsealed for the last five days. PA levels of 48 eighth-grade middle school students were measured using pedometers during physical education as well as outside of class over 10 school days. Measurements were made in both step count and exercise time. The mean 2,244 step count in physical education reflects a 17.2% contribution to the mean daily total of 12,993 steps. Mean exercise time per class of 21 min. constituted 58.3% of the total lesson, and 15.6% of the mean daily total. A 2 x 2 (BMI x Gender) MANOVA indicated significant main effects for gender, F(2, 43) = 6.73, p<.05, and BMI, F(2, 43) = 4.69, p<.05, favoring boys and students classified as having a healthy BMI. No significant interaction existed between the two. Tests of between-subjects effects showed both BMI and gender had significant effects on steps (p=.006 and .004) and time (p=.014 and .001), respectively. A two-tailed, paired t-test showed that neither step counts, t(8) = .75, p>.05, nor exercise time, t(8) = .49, p>.05, were significantly different between the sealed and unsealed days, suggesting minimal student reactivity to wearing pedometers. While physical education classes did provide a considerable amount of physical activity for the students, most PA is accrued beyond physical education, confirming the need for programs to make out-of-school PA a primary focus. Findings also align with previous studies regarding gender differences in PA, and ‘healthy' versus ‘at risk' populations.Keyword(s): assessment, measurement/evaluation, physical activity