Although preliminary results suggest that allogeneic hematopoietic stem cell transplantation (allo HCT) for ovarian cancer (OC) is a feasible procedure, the low patient number in previous studies had limited ability to evaluate the true benefit of allo HCT in OC. This retrospective multicenter study included 30 patients with OC allografted between 1995 and 2005 to determine the outcome of patients with OC treated with allo HCT. Prior to allo HCT, patients were in complete response (n 5 1), partial response (n 5 7), stable disease (n 5 11) or had progressive disease (n 5 13). An objective response (OR) was observed in 50% (95% CI, 33-67) of patients. Three patients of responding patients had an objective response following the development of acute graft-versus-host disease (aGvHD). The cumulative incidence of chronic GvHD (cGVHD) was 34% (95% CI, 18-50). Transplant relative mortality rates were 7 and 20% on day 100 and 1 year, respectively. With a median follow-up of 74.5 months (range 16-148), median progression free survival (PFS) was 6 months and median overall survival (OS) was 10.4 months. Patients who developed cGvHD following allo HCT had a significant OS improvement compared to those who did not (17.6 months vs. 6.5 months, p 5 0.042). However, PFS was not similarly significantly improved in patients who developed cGvHD (12 months versus 3.7 months, p 5 0.81). Allo HCT in OC may lead to graft-versus-OC effects. Their clinical relevance remains to be shown.Ovarian cancer (OC), the fifth-leading cause of death for women in the United States and Europe, is the most deadly of the gynecologic malignancies. 1 Current systemic therapy consists of a combination of carboplatin and paclitaxel. Even after extensive surgery and chemotherapy, up to 50% of patients suffer from relapsing disease. Median overall survival (OS) for patients after recurrence is $2 years. 2 To improve outcome, high-dose chemotherapy regimens have been tried usually based on carboplatin combinations. These appear to delay relapse but have no influence on OS. [3][4][5] Allogeneic hematopoietic stem cell transplantation (allo HCT) is an effective therapy for many hematological malignancies. The therapeutic benefit of allogeneic transplantation relies not only on high-dose chemotherapy administered before transplantation but also is largely related to an immune-mediated graft-versus-leukemia effect, due to transplantation of the donor's immune system along with the hematopoietic tissue. Recent data from experimental animal models and from preliminary clinical experience suggest that a graft-versus-tumor effect, analogous to the graft-versusleukemia effect, may be generated against solid tumors such as renal cell cancer, breast cancer and OC. 6 Regarding OC, immunotherapy agents such as systemic or intraperitoneal interleukin-2 7-9 and adoptive transfer of tumor-infiltrating lymphocytes 10 have been used with success, testifying to the