Aim. The prop ensity for certain individuals to develop staphylococcal recurrent furunculosis (RF) is not fully understood. But among the reasons of its development the immune system dysfunctions are described. As in the staphylococcus elimination the main role is played by neutrophils, the objective of this study was to determine nitric oxide (NO) and reactive oxygen species (ROS) production by polymo rphonuclear leukocytes (PMNs) of patients with RF and to compare them with the response of normal cells to stimulation.Materials and methods. The spontaneous and pyrogenal-stimulated nitric oxide production was evaluated in leukocyte cell cultures by Griess reaction, and ROS generation was determined in the stimulated and unstimulated NBT-test.Results. In this study we have demonstrated that leukocytes of healthy subjects respond on stimulation by the increase of both NO and ROS production. In contrast, leukocytes of patients with RF react by depression of NO formation at stimulation, and are characterized by decrease of ROS production reserve with the increasing of spontaneous ROS generation. Described disorders are revealed in the remission period as well as at exacerbation of furunculosis.Conclusion. The present study suggests that leukocytes of patients with RF have stable defect of stimulated NO production increase, which can be the reason for recurrent and severe course of furunculosis.