To estimate the impact of the 2009 A(H1N1) pandemic on hospital admissions in metropolitan France and the overseas territories, and to assess the value of data from the Hospital Information System (PMSI) for influenza surveillance, we compared PMSI data on hospital stays associated with influenza and pneumonia from 2009–2010 with historical data available since January 2007. In mainland France, the number of hospital stays for influenza increased fivefold during the pandemic, while stays in intensive care units (ICUs) increased tenfold, with 14,680 hospital stays during the pandemic, including 1,748 in ICUs. Similarly, hospitalizations for influenza with acute respiratory distress syndrome, those involving pregnant women, and those resulting in death were significantly higher during the pandemic. The average age of patients was 5 to 10 years younger than that observed during seasonal epidemics, whether for stays in intensive care or for all hospital stays combined. The length of stays, however, was similar. The peak in admissions occurred in December 2009. In the overseas territories, indicators for influenza hospitalizations followed a similar trend to those in mainland France. Activity peaks were staggered over time, occurring in August on Réunion Island, in September in French Guiana and Martinique, and in October in Guadeloupe. Data from the PMSI confirmed a marked increase in the number of hospitalizations and a greater severity of the pandemic influenza compared to seasonal influenza epidemics that occurred between 2007 and 2009. The tool is comprehensive but lacks responsiveness, even though during the pandemic, data were provided to the InVS within two months of the patient’s discharge. It complements other systems and thus helps consolidate their analyses. (R.A.)