To optimize the methods for determining neutrophil extracellular traps in peripheral blood and studying their level in the norm and in patients with candidiasis with inflammatory and erosive diseases of the upper gastrointestinal tract on the basis of the Institute of Gastroenterology of the National Academy of Medical Sciences and Clinical Association of Emergency Medicine, Dnipro, Ukraine, in 2019-2021. 42 patients with candidiasis with inflammatory and erosive diseases of the upper gastrointestinal tract were examined, including 10 women and 32 men aged 35-56 years, who made up the main group (MG). These patients were divided into two groups according to the results of microbiological examination of the mucous membranes of the gastrointestinal tract: group 1 consisted of 20 patients with oropharyngeal candidiasis of the oral cavity; Group 2 consisted of 22 patients with candidiasis in the esophagus and stomach with or without oropharyngeal candidiasis. The comparison group (ComG) included 9 patients without detection of yeast-like fungi. The control group (ConG) consisted of 25 practically healthy people (donors). Neutrophils were isolated from the leukocyte mixture on a double ficoll-verografin gradient. The resulting cells were incubated with E. coli, S. aureus, C. albicans. Control - neutrophils without activators. Cells were stained according to Romanovsky-Giemsa or acridine orange. A decrease in the level of NET was found in patients of groups 1 and 2 of the main group in relation to the control group and the comparison group. The results obtained showed that microorganisms induce the formation of neutrophil extracellular traps. The low level of neutrophil extracellular traps in patients indicates the inability of their neutrophils to form NET, which are important for antifungal protection, and the method of their determination can be used to analyze the functional state of neutrophils in various diseases.