This study is a randomized, double-blind, dose comparison study with an open-label cross-over segment that will assess the safety and efficacy of MDMA-assisted psychotherapy in veterans with chronic posttraumatic stress disorder. Twelve of 24 participants will receive the full dose of 125 mg, six will receive 75 mg and six will receive 30 mg (active placebo dose). An independent rater blind to condition will assess symptoms of PTSD and depression, general quality of life and posttraumatic growth prior to any psychotherapy sessions one month after the second experimental session.