Two isolates of Bacillus sphaericus (2013-4 and 2013-6) and one of B. thuringiensis H-14 (2013-9) from Romania were bioassayed in the laboratory against several species of Culicine and Anopheline mosquitoes. Second instars of Culex quinquefasciatus, Anopheles albimanus, An. quadrimaculatus and Aedes triseriatus exposed for 48 hr to the 2013-4 isolate responded with LC50 values of 0.0015, 0.187, 0.0527 and 0.0941 ppm of lyophilized primary powder respectively. Preliminary tests with 2013-4 against Psorophora columbiae indicated in LC50 of 0.0046 ppm. Similar results were obtained for the 2013-6 isolate against Cx. quinquefasciatus, An. albimanus and An. quadrimaculatus. Fourth instars of Cx. quinquefasciatus, Ae. aegypti, An. albimanus, An. quadrimaculatus and Ae. triseriatus exposed to a lyophilized primary powder of the B. thuringiensis isolate for 24 hr responded with LC50 values of 0.061, 0.074, 0.095, 0.161 and 0.151 ppm respectively. Exposure of fourth instars of Ae. triseriatus to 0.25, 0.5 and 1.0 ppm of 2013-9 In situ and subsequent incubation in the lab resulted in 34, 88 and 96% mortality respectively. In comparative tests of Bactimos primary powder, and 2013-9, relative toxicities of 5337, and 2345 ITU/mg were obtained. The B. sphaericus isolates compared favorably to other efficacious isolates reported in the literature.