A multicenter cohort study of 172 patients with follicular lymphoma and subsequent biopsy-proven aggressive histology transformation. Twenty-two patients (13%) underwent allogeneic HCT, 97 (56%) underwent autologous transplant, and 53 (31%) received rituximab-containing chemotherapy. Five-year progression-free survival in these cohorts were 46%, 55%, and 40%, respectively (p=0.12). In a multivariate analysis, patients treated with autologous transplant had improved overall survival (OS) compared with those who received rituximab-containing chemotherapy (hazard ratio [HR], 0.13; 95% CI, 0.05-0.34; p<0.001). There was comparable OS in patients treated with allogeneic HCT and rituximab-containing chemotherapy (HR, 0.44; 95% CI, 0.16-1.24; p=0.12).