This work presents an evaluation of the evidence for the antiquity of psychoactive plant use by the indigenous populations of the Central Andes. The first problem is to determine what constitutes clear archaeological evidence. The most direct form of evidence is the finding of plant remains in direct association with human activity. Another type of evidence is that provided by the implements used in the preparation and ingestion of psychoactive preparations. The most conclusive evidence of this type is that provided by the smoking pipes and by the snuffing paraphernalia. Psychoactive plant representations furnish a third type of evidence. Smoking pipes from NW Argentina and associated Anadenanthera seeds, dated to c. 2130 B.C., and snuff trays and tubes from the central Peruvian coast (c. 1200 B.C.), represent the most ancient use of psychoactive plants in South America. Chavin (c. 1000-300 B.C.), one of the most complex cultures during the formative period in Precolumbian Peru, clearly displays imagery directly related to psychoactive plant use in public monumental stone sculpture and architecture. San Pedro de Atacama, located in the desert of northern Chile, is the region with the most intensive use. Approximately 20-22% of the male population was using snuff powders between the third and the tenth centuries A.D. The great antiquity and its presence throughout the Central Andes, suggest an important role for psychoactive plants in the development of Precolumbian Andean ideologies. Key words: Hallucinogens; South America; Archaeology.