This article discusses the use ofpsychoactive plants in the Azapa Valley of northern Chile. The archaeological record of north ern Chile provides early and uninterrupted material evidence related to psychoactive practices involving the use of Anadenan thera as well as chemical evidence for the consumption of Erthroxylum. Therefore, we used gas chromatography and mass spectrometry to analyze the hair of 32 mummies of theMiddle period (ca. A.D. 500-1000) from the Azapa Valley. None of the analyzed cases tested positive for the consumption of Anadenanthera, but two tested positive for the ingestion of Banisteriopsis, a psychoactive plant prepared as an infusion generally called ayahuasca. We conclude that the consumption of Banisteriopsis in the Azapa Valley was related to therapeutic practices, such as those employed in childbirth and puerperium, rather than hallucinogenic.