Growth and repair of skeletal muscle are normally mediated by the satellite cells that surround muscle fibers, In regenerating muscle, however, the number of myogenic precursors exceeds that of resident satellite cells, implying migration or recruitment of undifferentiated progenitors from other sources. Transplantation of genetically marked bone marrow into Immunodeficient mice revealed that marrow-derived cells migrate into areas of induced muscle degeneration, undergo myogenic differentiation, and participate in the regeneration of the damaged fibers, Genetically modified, marrow-derived myogenic progenitors could potentially be used to target therapeutic genes to muscle tissue, providing an alternative strategy for treatment of muscular dystrophies.