Rain-water drainage basins are small, numerous, widely distributed in Abha City, Kingdom of Saudi Arabia. A preliminary larval survey revealed that, 21 out of 37 surveyed basins support mosquito breeding. Culex pipiens, was the most abundant mosquito species in basins. Basins supported mosquito breeding all the year round. Two formulations of Bacillus thuringiensis var. israelensis (Bti) viz., Culinex tablets, and Bacticide powder were evaluated for their efficacy against mosquitoes breeding in basins. Each basin was treated with the recommended dose of each formulation (One Culinex tablet or 0.5 gm of Bacticide powder) during April and July, 2002. Both formulations induced high larval mortalities for 48 hours post-treatments, but no residual effect was observed 1 weak post-treatment. In both treatments, Bacticide powder was more effective than Culinex tablets . The possibility of using both formulations by individuals or authorities for mosquito control in this particular breeding place has been discussed.