The use of hallucinogens as medicine has a long history as this was the dominant form of medicine in most premodern cultures. We have studied premodern medicine on the different continents and have been surprised over the level of knowledge and understanding we found in Peru, where the shamans, the Ayahuasqueros, seem to have an extraordinary high level of mastery of the use of hallucinogenic drugs as medicine. Ayahuasca, a mixture of two plants found in the jungle, has the hallucinogenic power similar to LSD-25, and because of an ingenuous pharmacological system its effect last as long as LSD, or even longer. We spent a month in Peru and travelled more than 1,500 km through the north of Peru and the Peruvian Amazonia in the attempt to find the most rational, safe and effective way to use Ayahuasca as medicine. We are content to report that a system with five consecutive days of Ayahuasca, supported by an Ayahuasquero trained in philosophy of life, allowed the patient to go deeper into the unconscious every day, followed by five days of silent reflection and contemplation is an extremely effective scheme for healing and possible the best way of using hallucinogens as medicine. It seems rational to use 150-500 µg LSD-25 in clinical research with hallucinogens as medicine as the dose and duration of the session seems to be difficult even for a trained shaman to control, when using Ayahuasca.