Mosquitoes are regarded as troublesome organisms worldwide due to their parasitic and pathogenic aspect causing malaria, yellow fever, dengue, West Nile and filariasis. Bacillus thuringiensis (Bt) products have effectively been used for decades in controlling the mosquito mediated diseases and also decreasing the chemical input into the environment. In the present study, biocontrol potential of previously characterized Bt SY49-1 strain was investigated on Culex pipiens larvae. Fourth instars of C. pipiens were subjected to spore/delta-endotoxins (50, 100, 250 and 500 mu g mL(-1)) of Bt SY49-1 strain, carrying cry genes active against Lepidoptera, Diptera, Coleoptera and Nematodes. The spore/delta-endotoxin mixture caused 100% mortality on the larvae at the dose of 500 mu g mL(-1). PCR results indicated that Bt SY49-1 harbors Lepidopter-Dipter specific cry2A gene as well as Lepidopter specific cry1Ab, cry1Aa/Ad, cry1C, cry9A, cry9C, Lepidopter-Dipter-Coleopter specific cry1B, and Nematode specific cry5 gene. Results indicated the potential usage of Bt SY49-1 in preventing the breeding of C. pipiens and the spread of diseases resulting therefrom.