The past decade has witnessed a dramatic increase in interest in the therapeutic application of psychedelic medicines including “classic” 5HT2A receptor agonists such as psilocybin and LSD, and associated medicines such as ketamine. This presentation will focus on research from our group examining mechanisms that might underly the actions of large (macro) doses of classic psychedelics and implications for psychedelic psychotherapy.  We will also examine new findings regarding the use of smaller (micro) doses of psychedelics for improving mental health and well- being. Finally we will explore the use of ketamine in mental health and the potential role of ketamine-assisted psychotherapy in the broader psychedelic landscape.