• Be a veteran (age 18-64 years old) who meets criteria for PTSD on the CAPS-5 (severity ≥ 25).

• Be fluent in speaking and reading English.

• Are willing to commit to medication dosing, therapy sessions, follow-up sessions, completing evaluation instruments, and all necessary telephone contact

• Be able to swallow pills.

• Agree to have study visits audio and/or video recorded, including MDMA session, assessments, and PE sessions, and aware that Independent Rater assessments for PE sessions will occur.

• Have a contact able to drive the participant home after the MDMA session.

• Provide a contact (relative, spouse, close friend, or other support person) who is willing and able to be reached by the investigators in the event of a participant becoming suicidal or unreachable.

• Agree to inform the investigators within 48 hours of any new medical conditions or procedures.

• If able to become pregnant (i.e., assigned female at birth, fertile, following menarche and until becoming post-menopausal unless permanently sterile), must have a highly sensitive negative pregnancy test at study entry and prior to the MDMA session, and must agree to use adequate birth control for 1 month before through 10 days after the MDMA session. Adequate birth control methods include intrauterine device (IUD), injected, implanted, intravaginal, or transdermal hormonal methods, abstinence, oral hormones plus a barrier contraception, vasectomized sole partner, or double barrier contraception. Two forms of contraception are required with any barrier method or oral hormones (i.e., condom plus diaphragm, condom or diaphragm plus spermicide, oral hormonal contraceptives plus spermicide or condom).

⁃ Agree to the following lifestyle modifications (described in more detail in Section 3.3 Lifestyle Modifications): comply with requirements for fasting and refraining from certain medications prior to and following the MDMA session, including a possible medication taper if on SSRIs, medications for ADHD, and/or other medications described in the concomitant medications section.

⁃ Agree not to participate in other PTSD psychotherapy during study treatment.

⁃ Not enroll in any other interventional clinical trials during the duration of the study, and commit to medication dosing, therapy, and study procedures.

⁃ At Pre-Screening, have at least moderate PTSD symptoms in the last month based on PCL-5 total score of 40 or greater (index).

⁃ May have well-controlled hypertension that has been successfully treated with anti- hypertensive medicines if they pass additional screening to rule out underlying cardiovascular disease.

⁃ May have asymptomatic Hepatitis C virus (HCV) that has previously undergone evaluation and treatment as needed.

⁃ May have alcohol or substance use disorder if participant is not in withdrawal or requiring detox. Participants must have a plan, agreed upon by investigator, therapy team, and study physician, to reduce use of alcohol or other substances and to manage symptoms without self-medicating. Enrollment will require that, in the judgment of the investigator, therapy team, and study physician, the plan for decreasing substance use is realistic and has a good chance of succeeding in order to prevent substance use from impacting the safety or effectiveness of the investigational treatment. Veterans will also be subject to a urine toxicology drug screening prior to enrollment and before the MDMA session.

⁃ May have a history of or current Diabetes Mellitus (Type 2) if additional screening measures rule out underlying cardiovascular disease, if the condition is judged to be stable on effective management, and with approval by the study physician.

⁃ May have hypothyroidism if taking adequate and stable thyroid replacement medication.

⁃ May have a history of, or current, glaucoma if approval for study participation is received from an ophthalmologist.