Introduction: Lyme borreliosis is an infectious disease caused by B. burgdorferi sensu lato and transmitted by a tick. In Slovenia it is highly endemic and common in children. A clinical sign of early disseminated and late disease is Lyme arthritis (LA). The aim of the study was to define demographic, clinical and laboratory characteristics of children with Lyme arthritis. Methods: The retrospective clinical study was carried out at the Department of Infectious Diseases, University Medical Center Ljubljana, Slovenia, from 2006 to 2013. The study comprised patients with Lyme arthritis younger than 15 years old. Lyme arthritis was defined by the clinical standards for the diagnosis, of Lyme borreliosis in Slovenia. The data was acquired from medical records via a questionnaire, and the infection was proven through microbiological testing of serum and synovial fluid. The patients were being followed up for six months. Results: 37 children were diagnosed with Lyme arthritis, their average age was8.7 years; girls were affected more frequently; cases were evenly distributed throughout the year; most patients come from Central Slovenia; less than one third of them recall a tick bite; less than half of the patients have the associated general symptoms of a borrelial infection; the knee is the most commonly affected joint, with pain being the most common local symptom. Confirmedand probable Lyme arthritis were diagnosed in 24% and 76% of the patients. Conclusion: As Slovenia is endemic for borreliosis, a prospective study of children with LA is required to understand the natural course of the disease, andshorten time to treatment.