Granular, liquid and briquette formulations of Bacillus thuringiensis var. israelensis were tested in small rice plots during 1984-88 against Psorophora columbiae larvae. Vectobac AS, Skeetal G, Teknar HPD, ABG 6172, ABG 6188, ABG 6193, ABG 6197, ABG 6199, ABG 6138F and ABG 6221 provided excellent control at high dosages and good control (generally greater than 85%) at relatively low concentrations. ABG 6221 and ABG 6172 provided excellent control at low concentrations. Additional testing of these formulations will be required to ascertain specific lower limits such that more economical larval mosquito control can be obtained.