New Mexico was the ﬁrst state to list post-traumatic stress disorder (PTSD)as a condition for the use of medical cannabis. There are no published studies, other than case reports, of the effects of cannabis on PTSD symptoms. The purpose of the study was to report and statistically analyze psychometric data on PTSD symptoms collected during 80 psychiatric evaluations of patients applying to the New Mexico Medical Cannabis Program from 2009 to 2011. Methods: The Clinician Administered Posttraumatic Scale for DSM-IV(CAPS) was administered retrospectively and symptom scores were then collected and compared in a retrospective chart review of the ﬁrst 80 patients evaluated. Results: Greater than 75% reduction in CAPS symptom scores were reported when patients were using cannabis compared to when they were not. Conclusions: Cannabis is associated with reductions in PTSD symptoms in some patients, and prospective, placebo-controlled study is needed to determineefﬁcacy of cannabis and its constituents in treating PTSD.