The influence of gamma-irradiation and radiosensitizer AK-2123 on secretion of reactive oxygen species (ROS) of human neutrophils was studied. gamma-Irradiation (from 5 to 25 Gy) of the neutrophil suspension inhibited spontaneous chemiluminescence and activated phorbol-12-myristate-13-acetate (PMA)-stimulated chemiluminescence. The time of maximum PMA-stimulated chemiluminescence amplitude was decreased with the dose range from 2 to 25 Gy. The addition of radiosensitizer AK-2123 depressed the early PMA-stimulated chemiluminescence response to gamma-irradiation. The obtained results suggest that this effect is connected with influence of AK-2123 on ion canals of neutrophils and may prevent the radiation-induced damage of blood cells.