BACKGROUND: Many factors affect the outcome of olfactory ensheathing cell transplantation for obsolete spinal cord injury, such as the time of injury, segment and sex. The best time to do olfactory ensheathing cell transplantation is unknown up to now. OBJECTIVE: To investigate the influence of time windows of olfactory ensheathing cell transplantation on the recovery of motion and sensation function in spinal cord injury patients. DESIGN: Self-control observation. SETTING: Department of Neurosurgery, Taian Disabled Soldier's Hospital. PARTICIPANTS: 135 patients with spinal cord injury were enrolled at the Department of Spinal Cord Surgery, Taian Disabled Soldier's Hospital of Shandong Province from June 2004 to June 2007, including 121 males and 14 females, aged 7-59 years, averagely 36 years. Duration of spinal cord injury included 0-6 months in 21 cases, 7 months-2 years in 71 cases and over 2 years in 43 cases. These patients or their guardians signed an informed consent of the cell transplantation. The experimental procedures were accorded with the rules of Ministry of Health of China (No. 91-006) and approved by the Taian Disabled Soldier's Hospital of Shandong Province. METHODS: ①Olfactory bulbs of aborted fetus were digested into single olfactory ensheathing cells, and then cultured for 7-15 days. Parturients signed the informed consent. This study was approved by the Hospital Ethical Committee. ②After general anesthesia, olfactory ensheathing cell suspension was implanted into the corresponding region by the multi-targeted injection with a microscope. According to the injury condition, targets generally located in upper or lower injured region and left or right normal spinal cord. The amount of targets depends on the size of the injured region. About 1 000 000 units of cells were injected into each target, about 50 μL of suspension, at 2×1010 L-1, 2-5 targets. ③American Spinal Injury Association impairment scale was used to assess the motion and sensation function in spinal cord injury patients before transplantation and 2-8 weeks after transplantation. MAIN OUTCOME MEASURES: Scores on American Spinal Injury Association impairment scale. RESULTS: 135 spinal cord injury patients were involved in the result analysis. Motion and sensation function was improved in spinal cord injury patients at different time windows compared with that before transplantation (P < 0.01). There was no significant difference in scores on motion and sensation function and the increased degree of the score at different time windows after transplantation (P > 0.05).CONCLUSION: Olfactory ensheathing cell transplantation can promote the recovery of nerve function in spinal cord injury patients, without the difference in time windows.