There are increasing concerns about the prevalence of childhood obesity, accompanied by a dramatic rise in Type II diabetes. It has been suggested that school physical education programs should play an important role in increasing children's physical activity levels, which would have a positive impact on children's health. Physical fitness testing is used in many school physical education programs, but often the fitness assessments used are performance-based tests. These are influenced by elements such as speed and agility that may be more reflective of natural ability than health status. It has been argued that these tests are not related to levels of physical activity or to other risk factors associated with physical inactivity. It is important to learn more about how health-related fitness assessments can be used as effective instructional tools, and that is the focus of this study. Specifically, the purpose was to examine the relationships between self-reported levels of physical activity and a health-related fitness assessment. Participants were 108 (53 boys and 55 girls) fourth and fifth grade children enrolled in a suburban public school. They participated in daily physical education classes. Research assistants trained to administer the assessments collected data. Fitnessgram (pacer, flexed-arm hang, curl-ups, body composition using calipers, and body mass index [BMI]) was used as the health-related fitness assessment, and the Physical Activity Questionnaire for Children (PAQ-C) was used to gather data regarding physical activity levels. The PAQ-C inventory asks children to indicate how many times in the previous week they participated in a wide range of physical activity behaviors across a variety of settings. Data were analyzed using a multiple regression analysis with aerobic fitness as the dependent variable and body composition, BMI, and PAQ-C as the predictor variables. The model accounted for 22% of the variance in aerobic fitness, with both body composition and PAQ-C making significant contributions. BMI did not enter into the model, consistent with recent research that suggests BMI may not be the optimal tool for assessing risk factors in children. The finding that self-reported physical activity levels account for a significant proportion of variance in aerobic fitness is promising. Children can understand concepts of being active and monitoring their physical activity levels. This supports the notion that, in conjunction with student activities such as physical activity logs and journals, Fitnessgram can be used as an effective instructional tool to help children increase their activity levels. Keyword(s): assessment, elementary education, physical activity