To compare the frequency and distribution of rearrangements in the dystrophin gene in Duchenne muscular dystrophy (DMD) between Japanese DMD patients and those in North America and Europe, Southern blot analyses of the dystrophin gene were carried out in 88 probands classified as DMD. Gene rearrangements were found in 61 (69%) subjects, and they were composed of partial gene deletions in 53 (60%) probands and partial duplications in 7 (8%) probands. A total deletion of the gene was found in 1 (1%) patient. Among 53 patients with deletions, 34 (64%) had breakpoints between introns 44 and 52 and 7 (13%) had breakpoints between introns 2 and 11. Both the frequency and the distribution of gene rearrangements found in this study were similar to those reported in North America and Europe. These data suggest that there are no ethnic or racial differences in the frequency and distribution of rearrangements thought to be caused by similar mechanisms in the dystrophin gene in all human racial groupings.