Insecticidal properties of protease inhibitors have been established in transgenic plants. In the wake of continuous research and rapid development of protease inhibitors it is important to assess possible effects on beneficial insects like the honey bee (Apis mellifera L.). In this study newly emerged caged bees were fed pollen diets containing three different concentrations (0.1%, 0.5% and 1% w: w) of soybean trypsin inhibitor (SBTI). Hypopharyngeal gland protein content, total midgut proteolytic enzyme activity of these bees, and survival were measured. Bees fed 1% SBTI had significantly reduced hypopharyngeal gland protein content and midgut proteolytic enzyme activity. There were no significant differences between control, 0.1% and 0.5% SBTI treatments. Bees fed a diet containing 1% SBTI had the lowest survival, followed by 0.5% and 0.1%, over a 30 day period. We concluded that nurse bees fed a pollen diet containing at least 1% SBTI would be poor producers of larval food, potentially threatening colony growth and maintenance. We also conducted further study in the field with similar objectives using micro nuc colonies. Results obtained were similar to the results that were obtained in the lab. In the field study, we measured some additional parameters like effects of SBTI on age of first foraging and larval development. There was significant difference in age of first foraging between control and 1% SBTI treatment.