Two wettable powders (Bactimos and Vectobac) and one flowable concentrate (Teknar) of Bacillus thuringiensis var. israelensis (B.t.i.) and primary powders of Bacillus sphaericus isolates 1593 and 2362 were evaluated (laboratory) against field-collected larvae of Anopheles gambiae s.l. and Culex quinquefasciatus in Ouagadougou, Burkina Faso. Bactimos, Vectobac and a Corn-cob B.t.i. formulation (ABG-6138G) were field tested against Cx. quinquefasciatus and An. gambiae s.l. The isolates of B. sphaericus were also tested against An. gambiae s.l. in artificial ponds. Both wettable powders of B.t.i. showed superior activity than the flowable concentrate formulation against An. gambiae s.l. in the laboratory. Culex quinquefasciatus was more susceptible (3-4X) to B.t.i. (Bactimos) than An. gambiae s.l. The isolates of B. sphaericus were more effective (2-3X) against both mosquito species than Bactimos. In a ditch and two channels, Bactimos, Vectobac and ABG-6138G at 0.65, 1.5 and 5.6 kg/ha, respectively, gave 91-100% control of Cx. quinquefasciatus within 3 days of treatment. The same formulations at rates ranging from 0.25 to 5.6 kg/ha, produced 82-97% control of An. gambiae s.l. in rainwater pools 24 h after treatment. Isolates 1593 and 2362 at 0.12 and 0.24 kg/ha gave excellent control of An. gambiae s.l. in artificial ponds.