The transformation of follicular lymphoma (FL) to high-grade histology occurs in up to 70% of patients. The role of hematopoietic stem cell transplantation (HSCT) in transformed FL is poorly defined. Twenty-four FL patients with histologically confirmed transformation to diffuse large B-cell lymphoma underwent unpurged autologous HSCT at our institution. Their median age was 56 yr. The median number of prior chemotherapies was 2 (range 1-6). Thirteen patients had residual nodal disease measuring more than 2 cm and four patients had bulky disease at the time of HSCT. Six patients had refractory disease at transplantation. At a median follow-up of 38 months, 3-yr progression-free survival following autologous HSCT was 40%. The 3-yr overall survival was 52%. The cumulative incidence of relapse and non-relapse mortality rate was 41% and 25%, respectively.