Allogeneic hematopoietic stem cell transplantation (allo-SCT) is a therapeutic option for adult patients with T-cell ALL (T-ALL). Meanwhile, few allo-SCT data specific to adult T-ALL have been described thus far. Specifically, the optimal myeloablative conditioning regimen is unknown. In this retrospective study, 601 patients were included. Patients received allo-SCT in CR1, CR2, CR 42 or in advanced disease in 69%, 15%, 2% and 14% of cases, respectively. With an overall follow-up of 58 months, 523 patients received a TBI-based regimen, whereas 78 patients received a chemotherapy-based regimen including IV busulfan-cyclophosphamide (IV Bu-Cy) (n = 46). Unlike patients aged. 35 years, patients aged <35 years who received a TBI-based regimen displayed an improved outcome compared with patients who received a chemotherapy-based regimen (5-year leukemia-free survival (LFS) of 50% for TBI versus 18% for chemo-only regimen or IV Bu-Cy regimens, P=10-5 and 10-4, respectively). In multivariate analysis, use of TBI was associated with an improved LFS (hazard ratio (HR) = 0.55 (0.34-0.86), P = 0.01) and overall survival (HR = 0.54 (0.34-0.87), P = 0.01) in patients aged o35 years. In conclusion, younger adult patients with T-ALL entitled to receive a myeloablative allo-SCT may benefit from TBI-based regimens.