Histological transformation from a follicular non-Hodgkin's lymphoma (NHL) to a higher grade lymphoma carries a poor prognosis despite treatment with aggressive anthracycline-based chemotherapy. We retrospectively analysed 35 patients with histologically transformed NHL who underwent high-dose therapy and autotransplantation at our centre. Patients up to 65 years old were eligible for autotransplant at the time of transformation or with subsequent relapses, provided that chemosensitivity to a salvage regimen could be demonstrated. All patients received high-dose therapy [etoposide 60 mg/kg, melphalan 160 mg/m2 and fractionated total body irradiation (TBI) 12 Gy] followed by unpurged autologous bone marrow or blood stem cell rescue. Most patients (69%) had advanced stage disease (stages 3--4) at transformation and bone marrow involvement was common (49%). Twenty-six (74%) patients were in partial remission (PR) and nine (26%) in complete remission (CR) at the time of transplant. Median duration from transformation to transplant was 10.9 months (range, 5.2 months--4.6 years). At a median follow up of 52 months after autotransplant, 19 (54%) patients had died. Causes of death were progressive lymphoma in nine patients (26%), treatment-related mortality (TRM) in seven (20%) and myelodysplasia in three (8%). Only five patients in our cohort were > 60 years old, but all died as a result of treatment-related causes (mostly pulmonary infections). Five-year overall survival and progression-free survival from time of transplant were 37% and 36% respectively. Using multivariate analysis of factors including gender, age, stage, extranodal disease, disease bulk, B symptoms, number of prior therapies, relapse status and CR/PR status at transplant, only advanced age significantly predicted for survival from autotransplant (P = 0.002). Our survival data are comparable to previous reports of autotransplantation for transformed NHL and suggest a benefit over standard chemotherapy alone in selected patients. However, our high TRM cautions the use of aggressive therapy, including TBI, in patients over 60 years old.