Vegetable farming with use of synthetic pesticides is practiced at Pahou and could implicate agricultural pesticides residues in the selection of this high resistance level. In addition, it is worth mentioning that the locality of Pahou is crossed by the Aheme Lake’s streams which sweep and converge several environmental pollutants and pesticide residues from the neighbouring peri-urban cities and farms to the coastal locality of Pahou. Although there is no evidence to date that pyrethroid resistance in adults An. funestus results from selective pressure in larvae, it could be different for DDT as this insecticide is more persistent in the environment than pyrethroids. Therefore, it is possible that several ranges of xenobiotics present in these water bodies around Pahou might have contributed also to the selection of this multiple resistance in An. funestusHowever, further investigations are needed to Torin 1 1222998-36-8 clearly elucidate the main factors contributing to the high levels of resistance recorded in this population of An. funestus. It will also be interesting to establish the geographical distribution of this DDT resistance across Benin. DDT resistance in An. funestus has been recently reported in Ghana, other West African country, but at a significantly lower level than in Pahou. Indeed, the mortality rate to 4% DDT observed in the An. funestus population of Obuasi region in Ghana was around 60 to 80% while no mortality was observed in Pahou. The present study reports the first case of pyrethroid resistance in An. funestus in Benin. However, this resistance is higher against permethrin than to deltamethrin. This resistance pattern is different to that observed in southern or East Africa where resistance to type II pyrethroid is higher than to type I. This difference may underline the existence of a different resistance mechanism for pyrethroid resistance in Benin compared to these regions. Moderate permethrin resistance was also detected in another West African An. funestus populations from Obuasi in Ghana but no pyrethroid resistance was reported in an An. funestus Soumossou in Burkina Faso indicating that this resistance may not yet be widely distributed across West Africa. The level of pyrethroid resistance observed in Pahou is also lower than the level observed in southern Africa notably in Mozambique where only 20% mortality was recorded after exposure of mosquitoes to 0.75% permethrin for 3 hours. Nevertheless, this resistance to pyrethroids is of great concern for malaria control programs with interventions based on LLINs as high level of resistance to this insecticide class is already widespread in An. gambiae, the other major malaria vector in Benin. Additionally, there is a risk that if such resistance is not managed properly, it can be further selected by ongoing control interventions such as the pyrethroid impregnated LLINs and IRS to a level that will seriously impact the success of future control programs.