Introduction - An outbreak of dengue fever 2 occurred in the western municipalities of French Guiana beginning in late November 2005. An investigation was conducted in Maripasoula in February 2006 with the objectives of confirming the outbreak, implementing an appropriate response, and documenting the arrival of dengue fever in the Haut-Maroni region. Methods - The methodology chosen was that validated by the Antilles-Guyana Interregional Epidemiology Unit. Definition criteria were used for suspected, probable, and confirmed cases. The entomological component consisted of an assessment of larval breeding sites and a quantification of vector presence in homes. Results - The survey involved 528 individuals (13.9% of the population). Among them, 127 were probable cases of dengue, whereas the surveillance system identified 6 confirmed cases. The study of larval breeding sites showed that these were present in all neighborhoods. Aedes aegypti were found in 90.9% of homes. Discussion - The dengue epidemic that affected French Guiana in 2006 began in the western part of the department. This is the first time a dengue epidemic has been reported outside the coastal municipalities. This investigation also provided a better understanding of vector populations. (R.A.)