Background: Patients with relapsed MCL remain incurable, especially if their tumors have a Ki-67 > 30%. We analyzed the long-term survival outcomes of 75 recipients of alloSCT. Methods: Patients were enrolled on 4 sequential protocols from 2005-2013; (80%) received the fludarabine, cyclophosphamide, rituximab-based regimen (Khouri et al, Blood 2012). Thirty-five (47%) patients also received alemtuzumab. Immunohistochemistry testing for Ki-67 was done on paraffin-embedded tissue sections of biopsy specimens that were obtained at last relapse pre-alloSCT. Results were assessed semiquantitatively. In addition, Ki-67 results in 20 cases were assessed by digital image analysis (Aperio Technologies, Vista, CA, USA). There were no discrepancies found between the 2 methods. Results: Sixty-seven (94%) of 71 biopsy specimens available were cyclin D1+ and 17 (23%) had blastoid morphology. Median age was 60 years and the median number of prior therapies received was 3 (range, 1-10). At the time of alloSCT, 67 (89%) had chemosensitive disease. A Ki-67 level of > 30% was found in 13 (38%) of 34 patients who had available samples. With a median follow-up time of 6.8 years (range, 2.1-14 years), the 5-year overall survival (OS) and progression free survival (PFS) rates were 49% and 37%, respectively. A plateau was observed after 5-years. A Cox model analysis was conducted for factors of interest including age, sex, International Prognostic Index (0 vs. > 0), LDH, PET, number of prior treatments, disease status, Ki-67, blastoid morphology, treatment with alemtuzumab, donor type, source of stem cells, and chimerism. Multivariate analysis showed that a higher number of prior treatments and mixed chimerism at day 100 were poor prognostic factors for both OS [HR 1.29, P = 0.007 and 2.4, (P = 0.01), respectively] and PFS [(HR 1.36, P = 0.002 and HR 3.14, (P = 0.0004), respectively]. There was no significant difference in OS according to Ki-67 of > or < 30% (P = 0.6). Conclusions: These long-term results suggest that alloSCT can overcome the negative prognosis of elevated Ki-67 and is curative in a significant proportion of patients with relapsed MCL, especially those with < 3 lines of therapy.