Allogeneic hematopoietic cell transplantation (HCT) can be curative for both myelodysplastic syndromes (MDS) and lymphoid malignancies. Little is known about the efficacy of allogeneic HCT in patients in whom both myeloid and lymphoid disorders are present at the time of HCT. We analyzed the outcomes in 21 patients with MDS and concurrent lymphoid malignancy when undergoing allogeneic HCT. A total of 17 patients had previously received extensive cytotoxic chemotherapy, including autologous HCT in 7, for non-Hodgkin lymphoma (NHL, n=7), Hodgkin lymphoma (HL, n=2), CLL (n=5), NHL plus HL (n=1), multiple myeloma (n=1) or T-cell ALL (n=1), and had presumably developed MDS as a consequence of therapy. Four previously untreated patients had CLL. A total of 19 patients were conditioned with high-dose (n=14) or reduced-intensity regimens (n=5), and were transplanted from HLA-matched or one Ag/allele mismatched related (n=10) or unrelated (n=9) donors; two patients received HLA-haploidentical related transplants, following a modified conditioning regimen. Currently, 2 of 4 previously untreated and 2 of 17 previously treated patients are surviving in remission of both MDS and lymphoid malignancies. However, the high non-relapse mortality among previously treated patients, even with reduced-intensity conditioning regimens, indicates that new transplant strategies need to be developed.