We provide estimates of medical care utilization and expenditures for children and young adults younger than age 30 with muscular dystrophies in the United States. Accurate estimates are essential for calculations of lifetime costs and for economic evaluations of screening and management strategies for muscular dystrophy. We compare the medical expenditures for persons with muscular dystrophy with others by age groups. The incremental annual expenditures of medical care for privately insured individuals with muscular dystrophy relative to others in 2004 averaged $18 930 and ranged from $13 464 at ages 5 to 9 to $32 541 at ages 15 to 19. Individuals with muscular dystrophy had average medical expenditures 10 to 20 times greater than individuals without muscular dystrophy. Individuals aged 15 to 19 years had the highest number of inpatient admissions related to respiratory infections and cardiac complications. The findings underscore the need for appropriate treatment options for individuals with muscular dystrophy as they age.