Physicians know that their patients can react differently to the same medical treatment: for some of them, the drug will prove inefficient, whereas for others it might provoke side-effects, sometimes rather serious. Such differences in response to drug intake are due to several factors, of which molecular variations in specific genes, named " ADME " (Absorption, Distribution, Metabolism, Excretion). This project aims at investigating the evolutionary mechanisms responsible for the diversity of ADME genes in human populations. Because of their role at the interface between the organism and its chemical environment, ADME genes are likely targets of recent selective pressures linked to changes in the environments in which humans evolved, such as changes in dietary habits for instance.