In 2002, the Centers for Disease Control and Prevention (CDC) awarded four sites - Arizona, Colorado, Iowa and New York - cooperative agreements (RFA 02172) to develop a surveillance network, the Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet). The overall objectives are: 1) to conduct active, population-based surveillance of Duchenne and Becker Muscular Dystrophy (DBMD) to characterize the epidemiology of DBMD and its complications and 2) to develop long-term follow-up and tracking of children with DBMD to describe the history and outcome of treated cases and/or those cases with treatments not consistent with protocol standards. The hypothesis guiding this research is that population-based surveillance and integrated research programs are effective in determining the prevalence of DMD/BMD disorders and establishing data on health outcomes and the types of care for these disorders. Research has shown that population-based surveillance for individual disorders is an effective first step to clinical and descriptive studies. Surveillance provides population data as a basis for making comparisons to the samples of individuals with these disorders that respond to questionnaires or clinical studies. The alternative of volunteer-based research in clinic-based populations may produce data that do not reflect the population of individuals with the disorder. For the current project, the Arizona Muscular Dystrophy Research and Surveillance Program (Arizona MD STARnet) proposes to continue as a participating MD STARnet site with the following specific aims: 1. Generate population-based prevalence and incidence rates for DBMD in the United States with particular attention to differences in rates over time and by race/ethnicity;2. Identify the early signs and symptoms of DBMD;3. Describe the medical and social services received and quality of life of families of patients with DBMD and whether these vary by race/ethnicity and socioeconomic status;and 4. Investigate whether the severity or course of DBMD is influenced by variation in type of care received and by type of mutation identified.