Biomonitoring makes it possible to track the presence of environmental pollutants and their effects on the body. It is currently in high demand among the general public. Public health officials rely on it because they need accurate estimates of exposure to these pollutants in order to improve public health decisions. Rapidly evolving, biomonitoring is a powerful tool for characterizing population exposure by integrating various sources. It does, however, have certain limitations, notably the lack of available biomarkers, as well as challenges related to ethical and logistical considerations and the interpretation of health impacts at the individual level. This is why biomonitoring requires clear communication regarding its objectives and limitations. The objective of a nationwide biomonitoring study is to describe and analyze population exposure levels to various pollutants, particularly to establish reference values, identify populations that are particularly exposed or sensitive, track trends over time, and guide risk management measures. The French Institute for Public Health Surveillance has been conducting biomonitoring activities for over 10 years. For example, in French Guiana, studies measuring mercury in hair have identified particularly exposed Amerindian populations, demonstrated the contribution of certain fish consumption to exposure, and assessed its consequences on child development. Another study examined dioxin exposure among populations living near incinerators, which was more pronounced among farmers and consumers who had previously lived near incinerators using older technology. Starting in 2009, the National Nutrition and Health Survey will provide the first reference values for the French population’s exposure to a range of substances, as well as insights into the determinants of these exposures. One of the future challenges is to establish a sustainable French biomonitoring system linked to health data, by developing the analytical capacity of French laboratories within the framework of international harmonization. (R.A.)