They partook, in the dark of night, in strange ceremonies where the ingestion of a frighteningly bitter plant opened doors to invisible worlds. A few shamans were among them, chanting invocations all night long and implementing strange rituals involving smoke and perfumes. During the day, they carried on with the shamanic treatment and they worked. For a month, they participate in another type of ritual taking place two to three times a week : a group therapy, as it is known to the post-Freudian school in vogue in Europe and North America. Such experiments take place at Takiwasi, a drug rehabilitation centre in the Peruvian Amazon where local traditional shamanic treatments based on psychotropic « sacred plants », especially ayahuasca, are used. The author was part of the experiment, at night as patient, and in the day time as therapist. The paper asks several questions. Can two treatments so different from one another as are shamanism and western-style group therapy be made to work together, especially with drug abusers? Is it possible, or indeed desirable, to bring patients into simultaneous contact with two types of treatment that rely on radically different or even opposed, logics, cultures and paradigms? For what outcome? The paper presents incipient reflections on those issues based on an experiment in 1998.