42 patients with neuropathic pain related to spinal cord injury and disease took a placebo, 2.9%, and 6.7% delta 9-THC in a randomized order. The primary outcome was pain intensity, and patients were also assessed for allodynia, heat-pain threshold, response to painful stimuli, subjective psychoactive effects, spasticity, and vital signs. Patients also completed neuropsychological tests after taking the treatment. Results indicated that 2.9% and 6.7% delta 9-THC had significantly better analgesic effect compared to placebo, while the difference between the two doses was not statistically significant. Delta 9-THC was associated with significant psychoactive effects compared to placebo, but had no significant effect on allodynia, pain response to mild-to-moderately painful stimuli, or neuropsychological testing.