Bacillus thuringiensis (var. israelensis) serotype H-14 was tested for efficacy against Anopheles crucians larvae in small ponds at a golf course, a woodland lake and along the edge of a rice field. Two commercial formulations were tested ranging from 0.25 to 6.0 kg/ha (1.5 x 108 to 3.0 x 109 International Toxic Units/ha.). The higher rates (1.8 - 3.0 x 109 I.T.U./ha) reduced larval counts 80 - 100% in most tests. The lowest rates were always less effective. Variability between test plots was large. Differences in larval reduction between application rates were not statistically significant.