The identification of dystrophin as the defective protein in patients with Duchenne and Becker muscular dystrophies (DMD and BMD) has allowed the development of sensitive and specific tests to establish a diagnosis and to aid in genetic counseling and prenatal diagnosis. The Basic Protocol describes three complementary multiplex PCR assays that detect 26 dystrophin gene exons. The multiplex nature of these assays allows the detection of up to ten different exons in a single reaction. At least one of these exons is missing in >95% of deletions. The Support Protocol describes preparation and storage of stock PCR reaction mixes with primers for each of the three diagnostic assays. The Alternate Protocol is a modification of the Basic Protocol for radioactive detection of duplications in males and deletions in carrier females.