This report outlines the approach taken by the French Institute for Public Health Surveillance (InVS) in collaboration with its various partners during the 2009 influenza A(H1N1) pandemic. Its content is based on the consolidation and compilation of various documents produced during and after the pandemic. While it is not intended to provide a specific analysis of each document produced, it aims to describe, in a factual manner, the various actions carried out by the InVS, from the emergence of the A(H1N1) virus in 2009 through the various phases of surveillance and analysis, up to the results of specific studies published more recently. (R.A.)