The effect of a diet containing the fruits of genetically modified cucumber plants expressing thaumatin on the non-specific resistance parameters of the consumer was determined. For five weeks 24 laboratory rats allocated to 3 groups were fed freeze-dried isoproteinous diets containing 15% transgenic or non-transgenic cucumber fruits of the same variety, or a standard mixture. The phagocytic activity of neutrophils and monocytes was determined by flow cytometry (Phagotest and Bursttest). Feeding transgenic cucumber caused a statistically significant increase in neutrophilic granulocytes that activated oxidation processes after stimulation of PMA and fMLP. The fluorescence intensity of neutrophils was higher when E. coli was used as the chemotactic agent.