Introduction. Various epidemiological surveillance systems for chikungunya and dengue viruses are in place in metropolitan France, depending on whether or not the Aedes albopictus mosquito—the vector for these two arboviral diseases—is present. Methods. These systems include mandatory reporting (DO), surveillance via a network of laboratories, and a regional enhanced surveillance system in departments where Aedes albopictus is established. Enabling regional and/or national surveillance, these systems use different notification or reporting criteria. They do not have the same level of comprehensiveness or the same objectives. Results. In 2011, 12 cases of chikungunya and 55 cases of dengue were subject to mandatory reporting. The number of cases in mainland France reported by the laboratory network was 34 for chikungunya and 276 for dengue. From May 1 to November 30, 2011—the period of activity for the mosquito vector—and in the departments where it is established, 17 imported cases of dengue and 4 imported cases of chikungunya were identified by the enhanced surveillance system and the laboratory network. No indigenous cases of chikungunya or dengue were confirmed in 2011. Conclusion. The number of imported cases of chikungunya and dengue in metropolitan France is primarily determined by the international epidemiological context and the flow of travelers from areas where these viruses circulate. With the vector’s spread to other metropolitan regions, consideration should be given to revising the plan to prevent the spread of chikungunya and dengue, taking into account available resources and the performance of surveillance systems. (R.A.)