Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are allelic disorders caused by mutations in the dystrophin gene. The molecular genetic analysis of these disorders is among the most difficult encountered in a routine diagnostic laboratory. The analysis is made difficult by the size and structure of the gene, which is 2.4 Mb in size, and comprises 79 exons encoding a 14-kb mRNA transcript (1, 2). The exons are all small (<200 bp), whereas the introns vary from 109 bp to >200 kb. The interpretation of results is hampered further by the incidence of new mutation (approximately one-third of DMD cases), the greater than normal level of recombination across the gene (approx 10% [3, 4]), and finally the occurrence of a significant level of germline mosaicism (5, 6).