Stem cells are a potential means of tissue regeneration in the brain that hold promise for treatment of the large number of stroke survivors who have permanent disability. Animal studies with stem cells derived from many different sources indicate that cells can migrate to the site of ischaemic injury in the brain, and that some survive and differentiate into neurones and glia with evidence of electrical function. Cells additionally promote endogenous repair mechanisms, including mobilization of neural stem cells resident within the adult brain. Whether the behavioural benefits seen with stem cell administration in rodent models reflect enhanced endogenous recovery or tissue regeneration is unclear. Production of stem cells to clinical standards and in quantities required for clinical studies is technically challenging. To date only a handful of patients have been involved in preliminary clinical studies of cell therapies for stroke, and there are therefore insufficient data to draw conclusions about either safety or efficacy. Further trials with several cell types are ongoing or planned, including neural stem cells, and bone marrow-derived stem cells and endothelial progenitor cells.