Mesenchymal stromal cells (MSC) are multipotent and self-renewing cells. MSC are studied for their in vivo and in vitro immunomodulatory effects, in the prevention or the treatment of isehemic injury, and for their potential properties of tissue or organ reconstruction. Over the last few years, the potential role of MSC in organ transplantation has been studied both in vitro and in vivo, and their properties make them an ideal potential cell therapy after solid organ transplantation. A prospective, controlled, phase 1-2 study has been initiated at the CHU of Liege, Belgium. This study assesses the potential risks and benefits of MSC infusion after liver or kidney transplantation. Even if the preliminary results of this study look promising, solely a prospective, randomized, large scale, phase 3 study will allow the clinical confirmation of the theoretical benefits of MSC in solid organ transplantation.