The aim of this dissertation is to study how, in the aftermath of the Conquest of America, Europeans have appropriated medicinal plants from Mexican, Caribbean, Andean, or Amazonian origin. 18th century European practitioners frequently used substances such as Peruvian bark, ipecacuanha, gaiacum wood, or chocolate – which reveals the extent of the phenomena, yet masks its complexity. Using an American remedy in Europe indeed implied many processes. Crucial to this research are: the sampling and growing of plants; the transmission of indigenous knowledge and its translation by allogenous; the drug trade across the Atlantic; experiences carried out on remedies; and expeditions conducted in America between the 16th and the 18th centuries. More than a “contribution” of America to Europe, this phenomenon of appropriation must be understood as a modality of colonialism. As natural object, and at the same time as naturalistic and medical knowledge, medicinal plants took on a political stake after the Conquest of America. For instance, while in 1570 they had been the target of one of the first scientific expeditions in history, in the middle of the 18th century they also led the Spanish crown to undertake various monopolistic projects. On the other side of the Atlantic, it was at the heart of conflicts between the “Indian” and the Spaniard, when the latter forbade the former from using abortive or hallucinogenic plants, and when the former refused to transmit his pharmacological knowledge to the latter.