Physical education (PE) should engage students in health-enhancing physical activity (PA, McKenzie & Kahan, 2004; Pate et al., 2006), and instill lifelong PA habits (NASPE, 2004) via quality instruction. Middle school students should be active for a significant portion of a PE lesson (e.g., 50%; NASPE, 2001; Pate et al., 2006). The purpose of this study was to determine the prevalence of middle school students achieving the recommended minimum amount of PA in PE and explore possible correlates of PA guideline compliance. Study aims were to: (1) examine the stability reliability of PA measurements, (2) determine the prevalence of students meeting the PE PA guideline, and (3) examine the influence of gender, body mass index (BMI, kg/m2), ethnicity, and lesson liking on PA guideline compliance. Participants were 2087 seventh- and eighth-grade students in the U.S. Pedometer (Yamax SW200) steps/min (i.e., total lesson steps divided by lesson time) data were collected during three PE classes in which 1798, 1851 and 1798 steps/min data points were collected during lessons one, two and three, respectively. A total of 1461 participants had steps/min data for all three lessons. The pedometer steps/min cut point of 82 was used as the PA guideline (Scruggs, 2007). BMI was stratified into normal weight (<95th percentile) and overweight (Ан95th percentile) categories. Ethnicity was stratified into Caucasian and non-Caucasian. Liking was measured each lesson via a single item 5-point Likert scale. Liking was stratified into low (<3) and high (³3) categories. An intraclass correlation coefficient (95% CI) was used to examine stability reliability of PA. A mean PA score was calculated for participants that had 2 to 3 steps/min scores. Prevalence was expressed as a percentage. Odds ratios (OR) for gender, grade level, ethnicity, BMI, and liking (adjusted for all other factors examined) and 95% confidence intervals were computed using logistic regression. Alpha was set at .05. PA across the three lessons was moderately stable (R=.74, .72-.76). Overall, 23.9% of the sample met the steps/min guideline. Meeting the PA guideline was substantially associated with being a male (OR=3.37, 2.61-4.36) and not overweight (OR=2.97, 1.75-5.04). Ethnicity (OR=1.29, .97-1.71), grade (OR=1.01, .79-1.30), and liking (OR=.87, .63-1.20) were not substantially associated with meeting the activity guideline. The following conclusions are underscored: (a) steps/min measured over three lessons demonstrates moderate stability, (b) approximately 25% of the participants met the PA guideline, and (c) PE programming should specifically target female and overweight students' PA.Keyword(s): exercise/fitness/physical activity, physical education PK-12, research