Background: The current practice of caring for hospitalized patients with indwelling urethral catheters in Siriraj Hospital is to change the drainage bag every 3 days. In an extensive medical literature search, no evidence was noted to support this practice.Objective: The purpose of this study was to compare the incidence of catheter-associated urinary tract infections (UTI) in hospitalized patients with indwelling catheters who receive a drainage bag change every 3 days with the incidence of UTI in patients who receive no bag change.Design: This study was a randomized controlled trial.Participants and study procedures: Of the patients at Siriraj Hospital, 153 with an indwelling urinary catheter for at least 3 days were randomized to a 3-day drainage bag change or a no change regimen. A urine sample was obtained from each patient forculture every 7 days, on the day the catheter was removed, or the day the patient was suspected of having a UTI.Results: Of the 153 study patients, 79 were randomized to the 3-day bag change regimen, and 74 patients were in the nochange group. Both groups were comparable for all baseline characteristics. The incidence of symptomatic UTI was 13.9% in the 3-day drainage bag change group and 10.8% in the no change group (P = .7). The incidence of asymptomatic UTI was 36.7% in the 3-day bag change group and 36.5% in the no change group (P = .9).Conclusion: There is no evidence for the necessity of a bag change every 3 days at Siriraj Hospital; the urine bag can be left longer than 3 days. However, the appropriate frequency of urinary drainage bag change needs additional study because the sample size in this study does not rule out a false-negative result.