Dennis McKenna is an ethnopharmacologist who has studied plant hallucinogens for over forty years. He is the author of many scientific papers, and co-author, with his brother Terence McKenna, of The Invisible Landscape: Mind, Hallucinogens, and the I Ching, and Psilocybin: Magic Mushroom Grower's Guide. He holds a doctorate from the University of British Columbia, where his research focused on ayahuasca and oo-koo-hé, two hallucinogens used by indigenous peoples in the Northwest Amazon. He received post-doctoral research fellowships in the Laboratory of Clinical Pharmacology, National Institute of Mental Health, and in the Department of Neurology, Stanford University School of Medicine. In 1990, he joined Shaman Pharmaceuticals as Director of Ethnopharmacology, and in 1993 became the Aveda Corporation's Senior Research Pharmacognosist. Dennis has been an adjunct assistant professor at the Center for Spirituality and Healing at the University of Minnesota since 2001, where he teaches courses in ethnopharmacology and botanical medicine. He has taught summer field courses in Peru and Ecuador, and has conducted fieldwork throughout the upper Amazon. He is a founding board member of the Heffter Research Institute, a non-profit organization focused on the investigation of the potential therapeutic uses of psychedelic medicines.