Background: Mesenchymal stem cells (MSC) were shown to induce beneficial effects in animal models of neurodegeneration and in pilot human trials in multiple sclerosis and amyotrophic lateral sclerosis (ALS). Aim: An open-label, clinical trial to evaluate the safety and efficacy of repeated intrathecal administrations of autologous-MSC in ALS-patients. Methods: The study included 20 subjects (age: 20–70) with definite diagnosis of ALS and Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R) score of >20. The patients were treated with 1–4 intrathecal injections of MSC, at intervals of 3–6 months. The primary endpoints were safety and tolerability. Efficacy measurements including ALSFRS-R score and forced vital capacity (FVC), were assessed as secondary endpoints. Results: No serious adverse events were observed during the whole period of the trial. One patient withdrew from the study before the first injection. The monthly rate of progression in ALSFRS-R was ameliorated by more than 25% in 15/19 patients between the 1st and 2nd injection (mean improvement of 107.1%); in 11/12 between the 2nd and 3rd injection and in 8/10 between the 3rd and 4th injection. Overall, during the whole period till the last transplantation 13 patients had a >25% improvement in the slope of progression of ALSFRS-R (mean improvement of 47.4%, p 0.0038, Wilcoxon rank signed test). 7 out of 19 patients actually improved clinically (range of increase in ALSFRS-R: +1 to +4 degrees) after the first transplantation and 5 remained improved after the second cycle. The response rate correlated with the time-intervals between the injections. Conclusion: The results of our study show that repeated intrathecal injections of autologous MSC was safe in patients with ALS and provide indications of medium-term clinical benefits that were related to the intervals between the administrations of the cells. Larger studies are needed to confirm these observations.