Graft-versus-host disease (GVHD) is a principal cause of morbidity following allogeneic hematopoietic cell transplantation (HCT). Standard therapy for GVHD, high-dose steroids, results in complete responses (CRs) in 35% of patients. Because tumor necrosis factor-alpha (TNFalpha) is an important effector of experimental GVHD, we treated patients with new-onset GVHD with steroids plus the TNFalpha inhibitor etanercept on a previously reported pilot trial (n = 20) and a phase 2 trial (n = 41). We compared their outcomes with those of contemporaneous patients with GVHD (n = 99) whose initial therapy was steroids alone. Groups were similar with respect to age, conditioning, donor, degree of HLA match, and severity of GVHD at onset. Patients treated with etanercept were more likely to achieve CR than were patients treated with steroids alone (69% vs 33%; P < .001). This difference was observed in HCT recipients of both related donors (79% vs 39%; P = .001) and unrelated donors (53% vs 26%; P < .001). Plasma TNFR1 levels, a biomarker for GVHD activity, were elevated at GVHD onset and decreased significantly only in patients with CR. We conclude that etanercept plus steroids as initial therapy for acute GVHD results in a substantial majority of CRs. This trial was referenced at www.clinicaltrials.gov as NCT00141713.