Insecticide resistance in Anopheles gambiae s.l is a major concern to malaria vector control programmes. In West Africa, resistance is mainly due to target–site insensitivity arising from a single point mutation. Metabolic-based resistance mechanisms have also been implicated and are currently being investigated in west Africa. The aim of this study is to better understand the origins of carbamate and organophosphate resistance in An. gambiae population from Atacora, Benin in West Africa.