There is a growing evidence during past a few years to show the primary features of the pathogenesis of Duchenne muscular dystrophy (DMD) which is the most common fatal Xlinked recessive disease of muscle in children. Complete cloning of the coding sequence for the DMD gene, and discovery of the gene product, dystrophin, is truly an epochmaking success in the history of DMD research. Dystrophin is a previously unknown protein which is now thought to be a membrane associated cytoskeletal protein (underlying the plasma membrane known in muscle as the sarcolemma) of muscle fiber. In DMD patients, the gene coding for dystrophin is defective, and hence the crucial protein is absent. Thus the genetic, biochemical and morphological basis of DMD have been elucidated greatly.To our surprise, although dystrophin lacked dog (CXMD) shows very severe clinical symptoms as observed in DMD patients, dystrophin lacked mdx mouse has no obvious clinical symptom. As recently reported, gene abnormality of mdx mouse is a single point mutation of the Dmd gene. And the premature termination of translation still possibly to produces truncated (115 kDa, and 27% in length) Nterminal dystrophin. Then the abnormal dystrophin may help the stability of the plasma membrane, and thus could produce the benign clinical course of mdx mouse. But this is unlikely, because the truncated dystrophin protein was not detected in mdx muscle when we used antibodies against the Nterminal regions. Therefore, in mdx mice, dystrophin defect can be compensated by the other protein (s) from dystrophin family, or by the better regenerating capacity and/or amount of fibrosis in muscle. Thus, probably we could find out a key for the theranv from mdx mice to improve the poor clinical course of DMD.An experimental myoblast transfer therapy for muscular dystrophy is truly one of the most important study for DMD research. In 1988, Partridge and coworkers injected normal mouse myoblasts into dystrophin defected mdx mouse, and successfully fused the injected myoblasts with the satellite cells from regenerating muscle fibers of mdx mice in 39 of 70 (55.7%) cases. And higher percentage of the myoblasts fusion was observed in the mdx/nude hosts group (79 %) than in the mdx hosts (47 %) . More importantly, the injected myoblasts did express normal dystrophin in the regenerated muscle fibers as much as 30 to 40 % of levels found in normal muscle, which would probably be enough to improve clinical symptoms. After that, Karpati and coworkers used clonal cultures of normal human myoblasts as the donor cells, and injected them into mdx leg muscles. The human myonuclei, which were radiolabeled before the injection, were incorporated into some of the regenerated mdx muscle fibers, and have expressed dystrophin at the surface membrane of the fiber with approximately 3 to 7 % of all fibers per muscle of a transverse section. Of course, we need to overcome several side effects including immune injection of implanted myogenic cells as indicated by Partridge et al. The most effective injection site, timing, i.e., age of the patient, and numbers of myoblast are also should be explored.