Mescaline, which can be derived from cacti such as peyote and San Pedro or chemically synthesised, has been used by humans for millennia for its effects ranging from anti-inflammatory and pain-relieving properties to healing wounds and in ritual ceremonies. Although currently a Schedule I drug, peyote and San Pedro are legal for use in some regions in the Americas for religious contexts in native communities owing to a longstanding tradition of use amongst indigenous peoples. As a Schedule 1 drug, however, it is regarded as having no recognised medical benefits and is deemed to present too much of a risk of physical and/or psychological abuse for it to be legally available for purchase or prescription. There are anecdotal reports of mescaline being used for a wide range of purposes, including analgesia and headache relief, yet no evidence exists for these yet. Only three clinical trials list mescaline as an intervention, one of which will investigate mescaline for alcohol use disorder. The other trials are investigating the effects of mescaline in comparison with other psychedelics, not against any particular condition, but as they affect a broad range of psychometric measures.