Two commercial preparations of thuringiensin, the β exotoxin produced by some strains ofBacillus thuringiensisBerliner, were tested for their effect on honey bees(Apis melliferaL.). ABG-6162 (ABG) and SAN410SC72 (SAN) were diluted in 50% sucrose. When bees were fed the toxin solutions throughout their life, only the most dilute preparation of ABG had no significant effect on LT50of replicate cages of bees when compared with untreated controls. All other dilutions of ABG and SAN significantly reduced LT50. A single feeding per bee of a 5 × 10−4dilution resulted in no significant reduction in LT50. for ABG. Higher doses and all doses of SAN caused a significant reduction in LT50. When dilutions in sucrose solutions were sprinkled on bees in cages, only the highest dose of ABG significantly reduced LT50. Lower doses of ABG and all doses of SAN had no significant impact on LT50. Based on low spray volumes and consequent high thuringiensin concentrations, it is possible but unlikely that foraging honey bees could be exposed to doses sufficient to reduce longevity. However, since sprays are water-based, it is unlikely that honey bees would be sufficiently attracted to it to consume a lethal dose. Furthermore, some spray volumes are large enough, and concentrations low enough, that no toxic effect is expected.