To find out the clinical effects of methylcobalamin on the conservative treatment of degenerative lumbar spinal stenosis, the study was carried out as a control single blind trial with 2 year follow-up in 152 patients, 68 males and 84 females, whose ages ranged from 55 to 85 years, average 67 +/- 18.1 years. They were randomly allocated into 2 groups, the control group, 82 patients, and the methylcobalamin group, 70 patients. All had classical history, and physical and radiographic findings which confirmed the diagnosis of spinal stenosis. Conventional management, including patient education, physical therapy and medication, were carried out in every patient and in addition methylcobalamin 0.5 mg was given orally three times a day in the methylcobalamin group for 6 months. All patients were followed up periodically for 2 years. Most of the patients in both groups showed improvement but there was no significant difference between the 2 groups in terms of pain improvement and neurological signs, except neurogenic claudication distance which was better in the M-group.