Although borreliosis was first described as a separate entity more than 20 years ago its pathogenesis still remains unknown. In recent years the role of pro- and antiinflammatory cytokines in the pathogenesis of borreliosis has been discussed. The purpose of the present study was to evaluate the role of IL-1beta, IL-18 and sIL-1RII in the development of early and late stages of borreliosis. The study group consisted of 60 patients divided into 3 groups: patients with erythema migrans, Lyme arthritis and neuroborreliosis. In all groups serum levels of IL-1beta, IL-18 and sIL-1RII were determined and in the patients with neuroborreliosis additionally in cerebrospinal fluid (CSF). The levels of cytokines and sIL-1RII were measured before the start of treatment and after its termination. Before the treatment the levels of IL-1beta, IL-18 and sIL-1RII in serum and CSF were significantly higher in all studied groups compared with the control. After the treatment, despite the regression of the clinical symptoms and significant reduction of initially high levels of the cytokines and sIL-1RII, only the levels of IL-1beta in all patients and the serum level of IL-18 in the patients with neuroborreliosis were comparable with the values in the control group. It could suggest that the inflammatory process was not inhibited completely and confirms the role of IL-1beta, IL-18 and sIL-1RII in the pathogenesis of borreliosis.