Dose-Response Study of MDMA-assisted Psychotherapy in People With PTSD

Inclusion Criteria: * Diagnosed with chronic PTSD for six months or longer. * Have a CAPS score showing moderate to severe PTSD symptoms. * At least one unsuccessful attempt at treatment for PTSD either with talk therapy or with drugs, or discontinuing treatment because of inability to tolerate psychotherapy or drug therapy. * Are at least 18 years old. * Must be generally healthy. * Are willing to refrain from taking any psychiatric medications during the study period. * Willing to follow restrictions and guidelines concerning consumption of food, beverages or nicotine the night before and just prior to each MDMA session. * Willing to remain overnight at the study site. * Are willing to be driven home after experimental sessions either by a driver they arrange, a taxi, or study personnel. * Are willing to be contacted via telephone by study personnel. * If of child-bearing age, must have a negative pregnancy and agree to use an effective form of birth control. * Must provide a personal contact who is willing to be reached in case of emergency. * Agree to let the investigators know within 48 hours of any planned medical interventions. * Are proficient in reading and speaking English. * Agree to have all psychotherapy sessions recorded. * Agree not to participate in any other interventional clinical trials during the course of the study. Exclusion Criteria: * Are pregnant or nursing, or if of child-bearing age and do not use an effective means of birth control. * Weigh less than 48 kg. * Meet DSM-IV criteria for substance abuse or dependence for any substance in the past 60 days. * Have used "Ecstasy" (material represented as containing MDMA) more than five times in the last ten years or at least once within 6 months of the MDMA session. * Are unable to give adequate informed consent. * Upon review of past and current drugs/medication, must not be on or have taken a medication that is exclusionary. * Upon review of medical or psychiatric history, must not have any current or past diagnosis that would be considered a risk to participation in the study.