Intravenous administration of human umbilical tissue-derived cells (hUTC) improves neurological function in young adult rats after stroke. However, stroke is a major cause of death and disability in the aged population, with the majority of stroke patients 65 years and older. The present study investigated the effect of hUTC on aged rats after embolic stroke. Rats at the age of 18-20 months were subjected to embolic middle cerebral artery (MCA) occlusion. Two groups of eight animals each were compared. The investigational group was injected intravenously with 1×10(7) cells/kg in serum-free culture medium (vehicle) 24 h after stroke onset, and the control group was treated with vehicle only at the same time poststroke. Intravenous administration of hUTC significantly improved neurological functional recovery without reducing infarct volume compared to vehicle-treated aged rats. Additionally, hUTC treatment significantly enhanced synaptogenesis and vessel density in the ischemic boundary zone (IBZ). Moreover, hUTC treatment resulted in a trend toward increased progenitor cell proliferation in the subventricular zone (SVZ) compared to vehicle-treated aged rats. Intravenous administration of hUTC improved functional recovery in aged rats after stroke. The enhancement of synaptogenesis and vessel density may contribute to the beneficial effects of hUTC in the treatment of stroke in the aged animal.