This study will examine the effects of MDMA-assisted psychotherapy in 12 people aged 18 or older who have received a diagnosis of advanced stage cancer (usually meaning inoperable and with metastases) who have anxiety as a result of this diagnosis that is either not helped by conventional anti-anxiety medication (such as Xanax or Valium), or who do not wish to take these medications because of their side effects. In Stage 1, all study subjects will receive an initial dose of MDMA followed by a second (supplemental) dose approximately two and a half hours later if the initial dose does not produce any problems. Eight of twelve study subjects will get 83.3 mg MDMA followed by 47.1 mg the first time, and 125 mg followed by 67.5 mg the second time. Four of twelve study subjects will receive 25 mg followed by 12.5 mg MDMA. Whether a person receives low doses or full doses of MDMA will be decided at random, as if by coin toss, and none of the researchers will know which dose of MDMA a person will get in Stage 1. The four subjects who received the lower doses of MDMA in Stage 1 may continue to participate into Stage 2 in which they repeat the study except that they will receive open-label 83.3 mg MDMA followed by 47.1 mg the first time, and 125 mg followed by 67.5 mg the second time. The eight participants in Stage 1 who had MDMA-assisted psychotherapy sessions at these higher dose strengths will not continue into Stage 2. The Stage 2 study extension will provide potential additional data on the MDMA doses being evaluated without having to recruit additional subjects.