SARS, heat waves, avian flu, bioterrorism—health risks seem to have taken on a previously unimagined scale in recent years. France, in particular, experienced a tumultuous 2003 in terms of health alerts. These events highlight the challenges that public health surveillance must now face—challenges for which it was not yet fully prepared. The Public Health Policy Act of August 9, 2004 (LPSP) demonstrates that these challenges have been recognized by affirming an ambitious operational commitment that brings the role of the Institute for Public Health Surveillance (InVS) to the forefront. The expertise expected of the InVS by the government is not limited to exceptional events. The law defines the priority public health plans for the next five years. The regions become the operational level for implementing these plans as well as for defining regional priorities. And the InVS plays a decisive role in this. (Introduction)