Because of its low content in rice, Cry1Ab/Ac protein was produced in Escherichia coli to obtain sufficient Cry1Ab/Ac protein for in vitro evaluation and animal studies to assess the potential safety of Cry1Ab/Ac protein in human food or animal feed. In order to use this safety package with transgenic crops expressing the Cry1Ab/Ac protein, examples of structural and functional equivalence of the microorganism-produced proteins used in the toxicology tests and the proteins produced in transgenic crops are demonstrated. It is an accepted approach for the safety assessment to compare the novel protein to common food allergens. Searches of the current amino acid sequence databases for homology with known allergens and for the presence of N-glycosylation sites provide other points of reference. Since most food allergens resist gastric digestion, the stability of the Cry1Ab/Ac protein under these conditions is also an important consideration. To have a direct assessment of the protein toxicity in mammals, an oral acute study in mice was used for evaluating the safety of the Cry1Ab/Ac protein.