Based on the good results of experimental transplantation in animal models of multiple sclerosis and of other autoimmune diseases, we have treated 24 patients suffering from chronic progressive multiple sclerosis with high-dose chemotherapy (BEAM regimen) followed by autologous blood stem cell rescue and antithymocyte globulin. Blood stem cells were mobilised with cyclophosphamide at 4g/m2 and G- (or GM-) CSF. In 9 cases, additional CD34+ cell-selection of the graft was performed. Here we update previously published results of this novel treatment, mainly with regard to clinical efficacy, as the median follow-up time has reached 40 months (range, 21-51). Infections were the principal toxicity early after the procedure, with death of a patient from aspergillosis 65 days post stem cell infusion. No serious late events occurred apart from a case of autoimmune thyroiditis that developed 11 months after transplant in a patient who had received a CD34+ cell-depleted graft. Mild and transient neurotoxicity was observed in 10 patients (42%), most probably associated with fever and infections. Eighteen patients (18/23; 78%) responded to the treatment, i.e., they were improved or stabilized, while five patients progressed, of which 4 had primary progressive disease. Of those improved or stabilised (18), 9 patients have maintained stable condition whereas 9 developed relapses or they slowly resumed progression, although their disability scores have not gotten worse than they were before transplantation. The probability of progression-free survival (compared to entry status) at 3 years is 92% for patients with secondary progressive disease and 39% for the primary progressive type. CD34+ cell-selection did not seem to yield better results except for a delay in progression or in relapse after transplantation. These results appear better than those achieved by any other treatment of progressive multiple sclerosis, including beta-interferon, but they need to be confirmed by other open or controlled studies in view of the well-known difficulty of judging objectively the effect of a treatment in patients with this disease.