More effective therapeutic strategies are required for patients with poor-prognosis systemic sclerosis (SSc). A phase 2 single-arm study of high-dose immunosuppressive therapy (HDIT) and autologous CD34-selected hematopoietic cell transplantation (HCT) was conducted in 34 patients with diffuse cutaneous SSc. HDIT included total body irradiation (800 cGy) with lung shielding, cyclophosphamide (120 mg/kg), and equine antithymocyte globulin (90 mg/kg). Neutrophil and platelet counts were recovered by 9 (range, 7 to 13) and 11 (range, 7 to 25) days after HCT, respectively. Seventeen of 27 (63%) evaluable patients who survived at least 1 year after HDIT had sustained responses at a median follow-up of 4 (range, 1 to 8) years. There was a major improvement in skin (modified Rodnan skin score, −22.08; P < .001) and overall function (modified Health Assessment Questionnaire Disability Index, −1.03; P < .001) at final evaluation. Importantly, for the first time, biopsies confirmed a statistically significant decrease of dermal fibrosis compared with baseline (P < .001). Lung, heart, and kidney function, in general, remained clinically stable. There were 12 deaths during the study (transplantation-related, 8; SSc-related, 4). The estimated progression-free survival was 64% at 5 years. Sustained responses including a decrease in dermal fibrosis were observed exceeding those previously reported with other therapies. HDIT and autologous HCT for SSc should be evaluated in a randomized clinical trial.