Cell therapy for degenerative muscle diseases such as the muscular dystrophies requires a source of cells with the capacity to participate in the formation of new muscle fibers. We investigated the myogenic potential of human fetal mesenchymal stem cells (hfMSCs) using a variety of stimuli. The use of 5-azacytidine or steroids did not produce skeletal muscle differentiation, whereas myoblast-conditioned medium resulted in only 1%-2% of hfMSCs undergoing muscle differentiation. However, in the presence of galectin-1, 66.1% +/- 5.7% of hfMSCs, but not adult bone marrow-derived mesenchymal stem cells, assumed a muscle phenotype, forming long, multinucleated fibers expressing both desmin and sarcomeric myosin via activation of muscle regulatory factors. Continuous exposure to galectin-1 resulted in more efficient muscle differentiation than pulsed exposure (62.3% vs. 39.1%; p < .001). When transplanted into regenerating murine muscle, galectin-1-exposed hfMSCs formed fourfold more human muscle fibers than nonstimulated hfMSCs (p = .008), with similar results obtained in a scid/mdx dystrophic mouse model. These data suggest that hfMSCs readily undergo muscle differentiation in response to galectin-1 through a stepwise progression similar to that which occurs during embryonic myogenesis. The high degree of myogenic conversion achieved by this method has relevance for the development of therapies for muscular dystrophies.