 Stroke is the leading cause of acquired adult disability. Except the hospitalization in stroke units, only thrombolysis has been shown to be efficient to treat acute ischemic stroke in the first three hours after the onset. Increasing brain plasticity after stroke represents an important alternative strategy. Cell therapy provides a functional improvement after cerebral ischemia in rodent models. This restorative therapy aims to replace destroyed cerebral tissue with a stem cells graft. Despite these encouraging experiments, we do not know yet the best way of administration of the stem cells, the best dose and the optimal delay of the graft. The pioneer clinical studies failed to reproduce this benefit for patients probably because of the limited number of studied patients. Therefore, more translational studies are needed to improve our knowledge in this promising field. Among different cell sources, mesenchymal or stromal stem cells MSC derived from bone marrow offer the advantage of arising from a non tumoral and no modified source and are not sources of immunological or ethical problems. 