For the past decade or so, INPES and OFDT have been measuring the prevalence and use of psychoactive substances through surveys of the general population. Conducted among the general population or younger age groups, these surveys make it possible to describe the diversity of these practices (experimentation, current use, regular use, etc.), assess their links to other factors, and conduct regional—or even departmental—analyses of this consumption. Above all, their regular repetition over time makes them a tool for monitoring changes in consumption patterns of various psychoactive substances. It is primarily the occasional use of the most common substances that is measured in general population surveys. Monitoring harmful use, dependence on illicit drugs, and the emergence of new drugs requires the use of complementary measurement tools, such as institutional statistics (from law enforcement and health agencies) and/or ethnographic studies and observations. The results of the 2010 Health Barometer, presented in this issue of *Tendances*, provide an update on the levels of use of various legal and illicit substances among the adult population, as well as trends in consumption since the results of the 2005 Health Barometer. Apart from contextual data covering the entire 11–75 age group, these initial results focus exclusively on the population aged 18–75 for alcohol and tobacco and 18–64 for illicit drugs, as other specific surveys are used for adolescents (ESCAPAD and ESPAD).