Although adipose tissue is an expandable and readily attainable source of proliferating, multipotent stem cells, its potential for use in regenerative medicine has not been extensively explored. Here we report that adult human and mouse adipose-derived stem cells can be reprogrammed to induced pluripotent stem (iPS) cells with substantially higher efficiencies than those reported for human and mouse fibroblasts. Unexpectedly, both human and mouse iPS cells can be obtained in feeder-free conditions. We discovered that adipose-derived stem cells intrinsically express high levels of pluripotency factors such as basic FGF, TGFbeta, fibronectin, and vitronectin and can serve as feeders for both autologous and heterologous pluripotent cells. These results demonstrate a great potential for adipose-derived cells in regenerative therapeutics and as a model for studying the molecular mechanisms of feeder-free iPS generation and maintenance.