38 patients with neuropathic pain related to spinal cord injury and disease were administered a placebo, 3.5%, and 7% delta-9-THC in a randomized order in this crossover trial. The primary outcome was pain intensity, secondary outcomes included allodynia, heat-pain threshold, response to painful stimuli, subjective psychoactive effects, and vital signs. Patients also completed neuropsychological tests after taking the treatment. Results indicated that 3.5%, and 7% delta 9-THC had significantly better analgesic effect compared to placebo, while the difference between the two doses of THC was not statistically significant. Delta 9-THC was associated with significant psychoactive effects and different neuropsychological test results compared to placebo, but had no significant effect on allodynia or pain response to mild-to-moderately painful stimuli.