A comparative analysis of the use of psychoactive plants in northern Chile, specifically San Pedro de Atacama and the Middle Loa and its tributaries (Caspana, Toconce, Lasaña, Chiu-Chiu), with NW Argentina, asaproba-ble diagnostic tool of shifting patterns of interaction. This work presents a review of the evidence for the ingestión of psychoactive plants in northern Chile and NW Argentina with particular emphasis on chronology, iconography and modes of ingestión. The iconographic and stylistic differences, as well as the divergence in chronology, suggest shifts in patterns of interaction between northern Chile and NW Argentina.