Dengue fever (DF) is a human arbovirus disease transmitted by the female mosquito of the genus Aedes, mainly Aedes aegypti, which is the most serious mosquito-borne viral disease worldwide and endemic in certain cities of Saudi Arabia, such as Jazan area. And because of the toxicity of the chemical- insecticides used in pest control programs, therefore, there is a need to use effective and safe alternative methods to eliminate pests. Therefore, the current study aimed to use the bacterium Bacillus thuringiensis as a bioinsecticide against the larval stages of Ades aegypti.
       Two formulationsof Bacillus thuringiensis var. israelensis (water-dispersible powder and Liquid formulation), were examined for their toxicity against immature and adult stages of Ades aegypti in the laboratory. Results indicated that the 50 % lethal concentration (colony forming unit, CFU) of B.t.israelensis against 4^th instars, was 8.31x10⁵CFUmL^-1in liquid formulation and 6.72 x10⁵CFU gm^-1for wettable powder.  Bioassay data also showed that pupation percent and adult emergence were affected more by subjecting the larvae to wettable powder than liquid formulation. The mortality values for the adults ranged between 49.33 & 64.23 % when using liquid formulation and wettable powder, respectively.