The regenerating skeletal muscle environment is capable of inducing uncommitted progenitors to terminally differentiate. The aim of this work was to determine whether adipose tissue-derived stromal cells were able to participate in muscle regeneration and to characterize the effect on muscle mass and functional capacities after transplantation of these cells. Adipose tissue stromal cells labeled with Adv cyto LacZ from 3-day-old primary cultures (SVF1) were autotransplanted into damaged tibialis anterior muscles. Fifteen days later, β-galactosidase staining of regenerated fibers was detected, showing participation of these cells in muscle regeneration. Two months after SVF1 cell transfer, muscles were heavier, showed a significantly larger fiber section area, and developed a significantly higher maximal force compared with damaged control muscles. These results are similar to those previously obtained after satellite cell transplantation. However, SVF1 transfer also generated a small amount of adipose tissue localized along the needle course. To minimize these adipose contaminants, we transferred cells from 7-day-old secondary cultures of the SVF1, containing only a small proportion of already engaged preadipocytes (SVF2). Under these conditions, no adipose tissue was observed in regenerated muscle but there was also no effect on muscle performances compared with damaged control muscles. This result provides further evidence for the existence of progenitor cells in the stromal fraction of freshly isolated adipose tissue cells, which, under our conditions, keep some of their pluripotent properties in primary cultures.