Abstract My fieldwork was conducted in Takiwasi, Centro de Rehabilitación de Toxicómanos y de Investigacíon de Medicinas Tradicionales in Tarapoto, Peru. The center combines psychotherapy with traditional medicine in treating in-patients with addiction problems to narcotic substances. The length of treatment for the patients is normally up to nine months. They also receive visitors coming to the center for a shorter period lasting from days to a few months. Most of the visitors I spoke with did not have addition problems, but often had other motives for coming to Takiwasi. Most of my informants came from Europe or The United States. I have a phenomenological perspective in this thesis, and my focus was to see how with their occidental background adhered, adapted to and experienced the treatment in Takiwasi. I also investigated how they understood and adapted to the ontology related to the treatment which is different from conventional treatment in the occidental world. The traditional medicine used in Takiwasi is plant based, where the clients and patients ingest plants often in ceremonies conducted by curanderos (shamans). Some of the plants have psychotropic properties that induce vivid visions and where the participants in the rituals experience forming bonds with spirits associated with the plants. I argue that Patients and visitors enter into a personalized relationship with some of the medical plants received in Takiwasi, and that the visions and experience the individual patients and visitors have with plants motivates them to make positive life changing steps, promoting their own health. At least the short term positive changes for some of the patients can be seen in forms of ending drug abuse and destructive behavior, increased respect for themselves, other people and nature, and an increased spiritual awareness. Key Words: ANT, spirituality, ayahuasca, plants, spirits, phenomenology, animism, medical anthropology, ontology, ritual, transformation.