Patients with amyotrophic lateral sclerosis (ALS) experience progressive and irreversible paralysis as a result of the continued loss of motor neurons, which leads to death in less than five years. To date, there is no treatment that can change the progression of this disease. Bone marrow stem cells have shown neural regenerative and neural repairing properties. Specifically, our group showed in a murine model of the disease that these cells, when injected in the spinal cord, can rescue motor neurons through the secretion of GDNF. Based on these results, we designed a phase I/II clinical trial for the purpose of demonstrating the viability of the intraspinal injection of autologous bone marrow mononuclear cells in patients with bulbar onset ALS, with an evolution between 6 and 36 months, with a forced vital capacity (FVC) 50% and T90 29%. This article describes the technique for extracting 60 mL of bone marrow used for the intervention, processing it by density gradient, and the neurosurgical technique used for implanting it. After 6 months of follow-up, the few adverse events reported in the first seven patients included seem to show that the procedure is safe and viable. Most of these patients, including two with a rapid deterioration, have stabilized the progression of their FVC and the neurologic scales measured. The data obtained so for seem to justify the design of new trials more oriented toward the efficacy of the procedure.