OBJECTIVES: The aim of this study is to determine the clinical-epidemiological characteristics of UTI, and to examine whether a correlation exists between clinical entity (expressed by clinical and laboratory indicators) and complicating factors (comorbidity, sex, tumor, foreign body), and to determine share of UTI patients in the total number of hospitalized infectious patients in the observed period. STUDY DESIGN: Retrospective epidemiological study. PARTICIPANTS AND METHODS: Taking into account the criterion of inclusion (clinically and laboratory-proven symptomatic UTI), the study included all hospitalized patients with UTI at the Clinical Hospital Center Osijek, at the Clinic for infectology in the period from June to December 2016. Clinical, demographic, microbiological, biochemical and hematological data was collected and analyzed using the history of hospitalized patients with UTI. RESULTS: UTI was diagnosed in 188 patients, predominantly elderly women. There were many factors that complicated infection Most patients had fever, fewer had other symptoms of UTI, like dysuria, pollakisuria, suprapubic or lumbar pain. More than 12% of the patients had positive blood cultures, and more than 1/3 of the patients had positive urine cultures. The most common isolate was E. coli. Patients with higher inflammatory parameters and the presence of complicating factors were, on average, hospitalized longer with average duration of hospitalization being 7,68 days. The outcome of the treatment was mostly positive, and lethal outcome was rare. CONCLUSION: Factors that require further effort in order to prevent these infections are incidence of UTI in daily clinical work, as well as significant comorbidity, and predisposing complicating factors. The key to success is their early detection and appropriate antimicrobial treatment.