Ten of 80 endospore-forming bacilli, isolated from various habitats of Jordan, were found to be highly toxic to the 4th instar larvae of Culiseta longiareolata (Macquart). The bacilli were identified into the following species and strains: Bacillus sphaericus (H6), B. sphaericus (H9a, 9b), B. cereus Frankland and Frankland, B. brevis Migula and B. megaterium Bary. Bacillus cereus comprised 50% of the isolates. The toxic concentrations of these isolates against C. longiareolata ranged between 1.2 x 10(7) and 1.1 x 10(9) viable spores ml-1.