A flexible dose of MDMA, followed by a supplemental half-dose unless contraindicated, is administered during the Treatment Period with manualized psychotherapy in two open-label Experimental Sessions spaced approximately a month apart. This 8-week Treatment Period is preceded by three Preparatory Sessions. During the Treatment Period, each Experimental Session is followed by three Integrative Sessions of non-drug psychotherapy. The Primary Outcome measure, the Clinician-Administered PTSD Scale (CAPS-5) is assessed by a blinded centralized Independent Rater (IR) pool multiple times throughout the study. The IR pool will be blinded to visit number and number of treatments received and will not have access to data collected by the sites during the active treatment period.