BACKGROUND AND OBJECTIVES: SMA1 is a genetic disease that leads to a progressive apoptosis of the second motoneuron and then to a complete paralysis. There are reports of efficacy of mesenchymal cells in the treatment of other neurological diseases; therefore we decided to treat some children with these cells. METHODS AND RESULTS: Four children suffering from SMA1 were treated by means of intrathecal injections of mesenchymal cells. All patients improved their motility after three weeks. The effect was relevant at the distal muscles, while the proximal ones were less affected. The treatment was repeated once a month for 3~8 months as the effect of the treatment lasted not more than 30 days. One patient who withdrew the treatment died after 45 days. Another patient resulted completely paralysed after two months after quitting the cell therapy but he regained the skills after a new injection. Two patients are stable after the first improvement. CONCLUSIONS: Intrathecal injections of mesenchymal cells improve the motility of children suffering from SMA1. We argue that an early treatment, before the onset of irreversible neurological damages, could result in the cure of this disease.