Prior therapy with rituximab might attenuate disparate histocompatibility antigen presentation by B cells, thus decreased the risk of acute graft-versus-host disease (GVHD) and improved survival. We tested this hypothesis by comparing the outcomes of 435 B-cell lymphoma patients who received allogeneic transplantation from 1999 to 2004 in the Center for International Blood and Marrow Transplant Research database: 179 subjects who received rituximab within 6 months prior to transplantation (RTX cohort) and 256 subjects who did not receive RTX within 6 months prior to transplantation (No-RTX cohort). The RTX cohort had a significantly lower incidence of treatment-related mortality (TRM) [relative risk (RR) = 0.68; 95% confidence interval (CI), 0.47-1.0; P = 0.05], lower acute grade II-IV (RR = 0.72; 95% CI, 0.53-0.97; P = 0.03) and III-IV GVHD (RR = 0.55; 95% CI, 0.34-0.91; P = 0.02). There was no difference in the risk of chronic GVHD, disease progression or relapse. Progression-free survival (PFS) (RR = 0.68; 95% CI 0.50-0.92; P = 0.01) and overall survival (OS) (RR = 0.63; 95% CI, 0.46-0.86; P = 0.004) were significantly better in the RTX cohort. Prior RTX therapy correlated with less acute GVHD, similar chronic GVHD, less TRM, better PFS and OS.