To investigate patient- and procedure-related factors associated with hospital re-admission (HR) and re-hospitalization following flexible ureteroscopy (f-URS). Patients and methods: The records of patients who underwent f-URS for renal stones in two reference centers between 2011 and 2015 were examined retrospectively. Patients who were re-admitted to the hospital or re-hospitalized for any reason within 30 days after hospital discharge related to the f-URS procedure were evaluated. The patient- and procedure-related factors affecting the re-admission and re-hospitalization rates were revealed using backward stepwise multiple binary logistic regression analysis.