Duchenne and Becker muscular dystrophies (DBMD) are X-linked disorders presumed to affect 1 in 3,500 male births. These conditions follow a course of progressive muscle weakness leading to death in the late teens to early twenties. As such, the impact of these conditions on medical systems, communities, and families is significant. Through the 'Muscular Dystrophy Community Assistance, Research and Education Amendments of 2001', the United States Congress enacted legislation to provide for research with respect to various forms of muscular dystrophy, including DBMD. A part of this Act authorized the creation of a National Muscular Dystrophy Epidemiology Program, in which the Secretary, acting through the Director of the Centers for Disease Control and Prevention (CDC), provided for a national surveillance program for DBMD for the purpose of carrying out epidemiological activities, including collecting and analyzing information on the number, incidence, correlates, and symptoms of those individuals with DBMD. To fulfill this mandate, in 2002, the CDC awarded four sites - Arizona, Colorado, Iowa and New York - cooperative agreements to develop a surveillance network, the Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet). MD STARnet sites have been developing and implementing epidemiologic methods that will lead to a better understanding of DBMD over the past four years. For the current project, the Colorado Department of Public Health and Environment proposes to continue as a participating MD STARnet site to: 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. We believe that the accomplishment of the objectives and activities above will be meaningful to both clinicians and families and will help to guide the development of standards of care for muscular dystrophy.