For the past decade, 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 help describe the diversity of these practices (experimentation, current use, regular use, etc.), assess links with other factors, and conduct regional or even departmental analyses of this consumption. Their regular repetition over time makes them, above all, 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 (law enforcement and health) 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 licit and illicit substances among the adult population, as well as changes in consumption since the results of the 2005 Health Barometer. Apart from contextual data on the entire 11–75 age group, these initial results then focus solely on the population aged 18–75 for alcohol and tobacco and 18–64 for illicit drugs, with other specific surveys used for adolescents (ESCAPAD and ESPAD).