Patients with T-cell and natural killer-cell lymphomas have poor outcomes. This study examined the role of allogeneic haematopoietic cell transplantation (allo-HCT) after nonmyeloablative conditioning in this setting. Seventeen patients with T-cell lymphoma or NK-cell lymphoma, including three patients in first complete remission, received allo-HCT after 2 Gy total-body irradiation and fludarabine. The median age was 57 (range, 18-73) years. The median number of prior therapies was 3 (range, 1-7), six patients (35%) had failed prior autologous HCT, and five patients (29%) had refractory disease at the time of allograft. Postgrafting immunosuppression was provided with mycophenolate mofetil with ciclosporin or tacrolimus. After a median follow-up of 3.3 (range, 0.3-8.0) years among surviving patients, the estimated probabilities of 3-year overall and progression-free survival were 59% and 53%, respectively, while the estimated probabilities of non-relapse mortality and relapse at 3 years were 19% and 26%, respectively. Sixty-five percent of patients developed grades 2-4 acute graft-versus-host disease and 53% of patients developed chronic graft-versus-host disease. Allo-HCT after nonmyeloablative conditioning is a promising salvage option for selected patients with T-cell and NK-cell lymphomas. These results suggest that graft-versus-T-cell lymphoma activity is responsible for long-term disease control.