Health promotion agenda (CDC, 1997; USDHHS/USDE, 2000) suggests to physical educators that children engage in moderate to vigorous physical activity (MVPA) for a large percentage of the lesson time. Given the expense of using heart rate monitors (HRM) as a means of quantifying MVPA in school settings, a more practical method of measuring MVPA is needed. In this study, the validity of the Yamax electronic pedometer as a means of assessing the percentage of lesson time spent in MVPA was investigated. Of secondary interest was the influence curriculum had on male and female physical activity levels as measured by HRM and pedometry. Thirty-one male (n=17) and female (n=14) students with a mean age of 11.08 (±.22) years wore HRMs and pedometers concurrently during physical education. MVPA was identified as heart rate values greater than 50% of student’s maximum heart rate reserve. Step intensity (STINT) of the lesson was calculated by dividing pedometer steps by lesson time. Each lesson was divided into a fitness segment (FS) and sport segment (SS). Data were collected over 13 consecutive school days. A Pearson r coefficient was used to examine the relationship between MVPA and STINT. Data revealed a modest correlation between STINT and MVPA, r=.308, p < .05. Independent t-tests were used to examine physical activity level gender differences between each lesson segment and for the overall lesson. Students averaged 2026 steps (±405) per class resulting in a STINT value of 52.79, and averaged 53.35% (±13.74) of the lesson time in MVPA. No gender differences were found for the overall lesson on the measures of MVPA and STINT. During the FS lesson segment males and females were found to be statistically equal for MVPA (56.36±14.21 vs. 58.21±11.32, p > .50) and STINT (52.66±11.25 vs. 54.54±10.43, p > .50) measures. However, during the SS lesson segment, males had significantly higher %MVPA (56.48±14.28 vs. 45.80±15.32, p < .05) and STINT (58.85±12.90 vs. 47.50±10.58, p < .05) values than females. Primary findings of this study were: (a) MVPA as measured by heart rate and STINT show only a modest positive correlation, and (b) curriculum influences physical activity level gender differences, especially for girls. These observations have significant ramifications for physical activity assessment and curricular decisions when valid assessment and maximizing physical activity are the objectives. The use of pedometry in physical education classes warrants further study, if heart rate telemetry accurately assesses MVPA in children.