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.