This pilot project was developed to investigate subjective and objective data related to the patterns of physical activity participation among hemophilia patients (FVIII or FIX) between the ages of 5 and 18 years. Physical activity participation among different levels of disease severity will be compared using accelerometers to calculate the amount of time spent in moderate to vigorous physical activity (MVPA) and the number of bouts of MVPA; additionally, data will be collected from two validated questionnaires (PedHAL and 3 day physical activity recall). Current literature that relates level of physical activity to disease severity in the pediatric hemophilia population is limited. The information gained about the type and quantity of physical activity participation in children with varying levels of hemophilia will assist in the development of education and interventions to promote good physical activity and potentially examine the role of tailored prophylaxis.