Intravenous (IV) cyclophosphamide is currently used in secondary progressive (SP) and Primary progressive (PP) Multiple Sclerosis (MS) but its efficacy remains uncertain. Furthermore, it is necessary to determine which MS should be successfully treated with IV cyclophosphamide. We retrospectively investigated 111 consecutive patients with progressive MS (21 PPMS and 90 SPMS) treated in an open label fashion with IV cyclophosphamide. We analysed clinical data (gender, age, duration of progression, primary versus secondary MS). The treatment response was assessed by EDSS change after 6 months and 1 year of treatment. The annual relapse average decreased from 1.92 before treatment to 0.39 during the treatment. Age and gender did not influence response to therapy. We did not find any difference of response between PPMS and SPMS. Duration of the progressive phase in SPMS was not a predictive factor of efficacy. A better response was noted in SPMS patients with surimposed relapses than in patients without relapses during the year before treatment (p<0.05). Furthermore, the better response in SPMS patients with relapses before treatment suggests that it is necessary to treat when MS is still in an inflammatory stage.