The purpose of this work was to evaluate phagocytosis and oxidative burst changes in neutrophils of patients with Lyme arthritis before and after antibiotic treatment. The examined patients were divided into three groups: group 1-18 patients with diagnosed Lyme arthritis, group 2-12 patients with Lyme arthritis after 14-day treatment with cefuroxime and control group--25 healthy individuals. The phagocytic activity of peripheral blood neutrophils (percentage of phagocytic cells and fluorescence) was measured using standard cytometric flow assay (Phagotest-kit, Orpegen Pharma). The oxidative metabolism (percentage of bursting cells and fluorescence stimulated by Escherichia coli and PMA) was measured using cytometric flow assay (Burst-test, Orpegen Pharma). The results were statistically analysed using Mann-Whitney test. Evaluation of phagocytosis demonstrated no changes in the percentage of phagocytic cells. But fluorescence increased significantly after treatment. The comparison of oxidative metabolism activity showed no changes despite E. coli and PMA stimulation. Parameters of phagocytosis and oxidative metabolism did not correlate with neutrophil count in analysed groups of patients.