In April- May 1977, while on Phase VII of the Alpha-Helix Amazon Expedition, 1976-1977, we had an opportunity to carry out ethnotoxicological investigations in the region of Pebas in Amazonian Peru, where the numerically most important Indians belong to the Witoto and Bora tribes. Many of these Indians, originally from the Colombian region of the Ríos Karaparaná and Igaraparaná, were transplanted to the Pebas region in the 1930's. Substantial populations still live in the Karaparaná-Igaraparaná region under Colombian jurisdiction, and there is still some contact between the several groups. Many of the Witotos in the Pebas area are now so acculturated that even the older men - although some know the kinds of Virola once employed for the drug - no longer are familiar with the relatively simple methods of elaborating the pellets for hallucinogenic use. The Boras, on the other hand, are some-what less acculturated and conserve many of their older tribal customs, notwithstanding the inroads of Western religious and civil influences. We were able to witness on several occasions the preparation of the Virola paste amongst a group of Boras living in Brillo Nuevo on the Rio Yaguasyacu, an affluent of the Rio Ampiyacu which, in turn, empties into the Amazonas at the town of Pebas. These Boras no longer take Virola, or cumala, as it is commonly known in Peru, for hallucinogenic purposes of witchcraft, but older members of the group still remember how their elders prepared and used the drug. Knowledge of the methods of preparation of the product has been handed down even to the younger generation. What has apparently often been forgotten, we found, is which of the sundry species of Virola in the forests of the region were chosen for their psychoactivity and which were eschewed. Consequently, we had the Indians prepare paste from all of the species available and later sorted them out chemically in the laboratory: some containing the active tryptamines, others lacking these indolic compounds. A phytochemical summary of these analyses will be the subject of a later paper. We are here interested primarily in outlining the methods employed in the elaboration of the paste and a comparison of these methods with those followed by the Witoto Indians of the same original geographic area.