Aim: Hospital-acquired urinary tract infection (HAUTI) is an important issue that causes morbidity/mortality. We present a prospective study to identify the risk factors of HAUTI in catheterized patients hospitalized in a paediatric surgery unit. Methods: Patients catheterized before/after surgery were evaluated. A total of 112 patients were followed up. Simultaneous urine analysis was conducted, and urine culture was obtained 0, 3, 6, 9, 12 days after catheterization. Patients taking antibiotics just before hospitalization or those who had urinary tract infections (UTI) just before catheterization were excluded. The age, sex, date of hospitalization, timing of catheterization, duration of catheterization, associating urinary tract anomalies, history of UTI, conditions at time of catheterization and antibiotic usage of patients were noted. The frequency of UTI and duration of catheterization were crossed. Patients catheterized during same period of time, who had UTI, were evaluated according to conditions at time of catheterization, associating urinary tract anomalies and antibiotic usage. Results: Patients who had positive culture results were catheterized longer (13.4±9.8 days vs 6±5 days, P=0.042). The duration of preoperative antibiotic usage was greater in cases with positive culture results (3.8±5.2days vs 0.8±4.8 days, P=0.003). The infection rate detected was higher in patients who were catheterized in units, rather than in an operating room (P=0.030). Conclusion: The most important risk factors of catheter-associated UTI (CAUTI) are increased duration of catheterization, inappropriate conditions during catheterization and preoperative antibiotic usage. Urinary catheterization is an important risk factor of HAUTI in paediatric surgery units. The length of catheterization and antibiotic usage should be much shorter, and conditions during catheterization should be strictly sterile in order to prevent CAUTI. © 2012 The Authors. Surgical Practice © 2012 College of Surgeons of Hong Kong.