On the 6^th of December 2013, the first Caribbean autochthonous cases were diagnosed in Saint-Martin, and two weeks later in Martinique while a DENV-2 and DENV-4 outbreak was ongoing. The two genotypes were circulating from january2013 to February 2014. Because of the ressemblance of the symptoms, the dengue outbreak was able to delay thedetection of the first cases of Chikungunya. Objective: The aim of this study was to search for cases of Chikungunya arisen before December 2013 in Martinique. Materiel and methods: Dengue PCR negative samples were tested for chikungunya RNA from December 18 to November1st, using the Real Star Chikungunya® kit from Altona Diagnostics. And we looked at the epidemiologic evolution of the dengue outbreak. Results: Chikungunya PCR was found positive for 11 patients between, November 6 and December 18.While the number of samples tested by dengue PCR were arising, 227 in November and 329 in December, the positivity rate decline from 18.4 to 10.6%. Discussion: Retrospectively, uncommon evolution of the epidemiological curves of dengueindicated that something wasoccurring. We found that more than one month before the first official case, Chikungunyawas circulating in Martinique. Several sporadic cases occurs on November. The study was conducted on patients attending to hospital facilities, this may be a bias. Conclusion: Emergence of Chikungunya was hidden by the dengue outbreak. New virus can emerge or spread all over the world, andsurveillance network, clinicians and virologists must be aware.