It is hypothesized that a one time experience with psilocybin will occasion dramatic shifts in consciousness and awareness that will lead to short-term (ie hours to days) and long-term (up to 6 months in this study, following the administration of the second dosing, either psilocybin or placebo) improvement in anxiety, depression, and pain associated with advanced cancer. The exact mechanism of action is unclear but based on studies done in the 60's using serotonergic hallucinogens in patients with advanced cancer, improvements in anxiety levels, mood and pain were reported. However, a treatment model developed by the famous British psychiatrist Humphrey Osmond, offers one possibility. In this model, serotonergic hallucinogens' therapeutic mechanism lies in their ability to allow the individual to access novel dimensions of consciousness and their efficacy or lack thereof relies on whether a transcendent and mystical state of awareness is attained. Another possible mechanism relates to what Dobkin de Rios and Grob have described as 'managed altered states of consciousness,' where the power of suggestibility, occurring in a safe setting, allows one to transcend a particular state of consciousness (i.e. anxiety and depression associated with advanced illness) as a means to facilitate emotional discharge and to manage irreconcilable conflict.