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Although having five different ways of transmission the vector-boe is the principal way of transmission of Chagas disease,which involves insects of the subfamily Triatominae (Hemiptera:Reduviidae).Nineteen of the 31 species that occur in Mexico are associated with humans,and all are capable of transmitting the disease.Pyrethroids are the insecticides recommended for the control of these vectors in Mexico.We determined the susceptibility to the pyrethroids deltamethrin and permethrin of peridomestic populations of Triatoma mazzottii Usinger and two populations of Triatoma longipennis Usinger in comparison with a reference strain for each species.Bioassays were performed for the determination of the LD50 for both field populations and reference strains.A maximum of 27 fold resistance to deltamethrin was observed in T.mazzottii,meanwhile,for permethrin,T.longipennis from Jalisco show the highest value of 3.19 fold.There was significantly increased activity ofesterases in field populations in comparison with their corresponding reference strain.The results of the search of kdr mutations related to the resistance to deltamethrin and permethrin in the evaluated species show the presence of mutations in the field populations,as is the case with individuals of T.mazzottii,for which the mutation was found A943V,and for the two populations of T.longipennis included in this study,we report the presence of the kdr mutation K964R.Evaluation of the various mechanisms involved in resistance to pyrethroids in triatomines from Mexico could guide us to the real justification for insecticide resistance monitoring.