Around half of patients with relapsed or refractory follicular lymphomas treated with allogeneic SCT achieve long-term progression free survival whatever the conditioning regimen. Because the median age of patients with follicular lymphoma is 55 years, a reduced intensity conditioning is the most appropriate option in this setting. The outcome of patients with a chemoresistant disease is usually poor because of a high toxic mortality. As a consequence, only patients with a chemosensitive disease will be included in this study. To further reduce the toxic mortality, it is critical to reduce the incidence of severe acute GVHD. A low incidence of acute GVHD could be obtained by the use of Rituximab before and after the transplantation as reported by the MD Anderson's experience in several hematological malignancies including follicular lymphoma. Their results are impressive in patients with follicular lymphoma with long-term survival of 85%. The favored hypothesis is a depletion of patient and donor B cells reducing the presentation of minor histocompatibility alloantigens. The benefit of Rituximab could also be explained by its anti-lymphoma effects that could compensate the putative reduction of a graft versus lymphoma effect due to a better control of GVHD.