Study design: Lithium has attracted much attention as a neuroregenerative agent for spinal cord injury in animal models. We hypothesized that the lithium can be beneficial to patients with spinal cord injury. The safety and pharmacokinetics of lithium has been studied in our earlier phase I clinical trial, indicating its safety. This is a phase II clinical trial to evaluate its efficacy on chronic spinal cord injury patients. Objectives: The aim of this study was to investigate the efficacy of lithium on chronic spinal cord injury patients. Setting: A major spinal cord injury rehabilitation center in Beijing, China. Methods: Randomized, double-blind, placebo-controlled 6-week parallel treatment arms with lithium carbonate and with placebo. A total of 40 chronic spinal cord injury subjects were recruited. Oral lithium carbonate was titrated or placebo was simulated to maintain the serum lithium level of 0.6-1.2 mmol l À1 for 6 weeks, followed by a 6-month follow-up. The functional outcomes and the neurological classifications, as well as the safety parameters, adverse events and pharmacokinetic data were carefully collected and monitored. Results: No significant changes in the functional outcomes and the neurological classifications were found. The only significant differences were in the pain assessments using visual analog scale comparing the lithium and the placebo group. No severe adverse event was documented in the study. Conclusion: The lithium treatment did not change the neurological outcomes of patients with chronic spinal cord injury. It is worth to investigate whether lithium is effective in the treatment of neuropathic pain in chronic spinal cord injury. Sponsorship: China Spinal Cord Injury Network Company Limited.