Dengue and chikungunya are two arboviruses that circulated extensively in 2006 in the French overseas departments, with dengue affecting the Caribbean region and chikungunya the Indian Ocean region. The results of a quantitative estimate of the number of cases in mainland France, based on data reported by laboratories, are presented here. In 2006, 783 imported cases of chikungunya and 228 cases of dengue were identified. The temporal distribution of chikungunya cases correlates with the epidemic in Réunion. Imported cases were detected throughout mainland France, with a clear predominance in the Île-de-France and Provence-Alpes-Côtes-d'Azur regions. These results show that the high number of dengue and chikungunya cases identified in mainland France in 2006 is correlated with the circulation of the virus in areas visited by travelers and, in particular, in the overseas departments. Given that the Aedes albopictus vector is established in southern France, the risk of introduction and local transmission of these arboviruses is real. For travelers visiting areas where these viruses circulate, in the absence of a vaccine or treatment, the importance of individual preventive measures should be emphasized.