Acute GvHD (aGvHD) is a life-threatening complication of hematopoietic stem cell transplantation. Frontline therapy for aGvHD consists of corticosteroid administration. However, ˜ 25% of the patients have a steroid-refractory disease, a sign of poor prognosis. An alternative therapy for steroid-refractory aGvHD is infusion of mesenchymal stromal cells (MSCs). Herein, we report the results of 46 patients treated with MSC infusion as salvage therapy for steroid-refractory aGvHD III/IV (78% grade IV). Patients received a median cumulative dose of MSCs of 6.81 × 106/kg (range, 0.98-29.78 × 106/kg) in a median of 3 infusions (range, 1-7). Median time between the onset of aGvHD and the first MSC infusion was 25.5 days (range, 6-153). Of the patients, 50% (23/46) presented clinical improvement. Of these, 3 patients (13%) had complete response, 14 (61%) had partial response and 6 (26%) had transient partial response. The estimated probability of survival at 2s year was 17.4%. Only 2 patients (4.3%) presented acute transient side effects (nausea/vomiting and blurred vision) during cell infusion. No patient had late or severe side effects because of MSC infusion. These results suggest that this therapeutic modality is safe and should be considered for steroid-refractory aGvHD, especially in countries where other second-line agents are less available.