This article examines the evidence for plant hallucinogenic use (possibly Brugmansia, Brunfelsia chiricaspi, Desfontainia R., Anadenanthera peregrina, Banisteriopsis sps, Psychotropia viridis and rola theidora) by the San Agustin culture, an extinct peoples who resided in the Magdelena River area of Colombia from the third century B . C . until the sixteenth century A.D. Based on thematic materials gathered from a cross-cultural survey of plant hallucinogens, the author examines themes in the monolithic sculptures of this culture in light of man-animal transformations and shamanic themes linked to plant hallucinogenic ingestion. Keywords-alter ego, plant hallucinogens, San Agustin monolithic sculptures, shamanism, shape­ shifting