AIM: To determine the role of ciprofloxacin in reducing cholangitis in cholestatic patients with adequate biliary drainage after endoscopic retrograde cholangiopancreatography (ERCP).METHODS: A randomized, controlled trial was performed in 48 cholestatic patients at Rajavithi Hospital (Tertiary Referral Center for ERCP: 600 cases per year). All the 48 patients received 200 mg ciprofloxacin intravenous injection for 30 min before starting any procedures, and then were randomly divided in two groups. Twenty-two patients in study group continually received ciprofloxacin until 48 h after ERCP. Causes of biliary obstruction, bacteriology of bile and blood (in cholangitis) and clinical cholangitis were recorded.RESULTS: Forty-eight patients were enrolled and divided into continuous ciprofloxacin treatment group (n = 22) and discontinuous ciprofloxacin treatment group (n = 26). During ERCP, stones were found in 22 patients,malignant diseases in 24 patients and other pathologic lesions in 5 patients. One (4.5%) of the 22 patients who received ciprofloxacin and 2 (6.3%) of the 26 patients who discontinued ciprofloxacin after ERCP developed cholangitis (relative risk = 0.71; 95% CI = 0.14-3.65;P = 0.88). Bacterobilia was found in 27 (56.3%) out of 48 patients. E. coli and Streptococcus viridans were the most common organisms.CONCLUSION: Continual use of ciprofloxacin in patients with cholestasis after adequate biliary drainage procedures plays no role in reducing cholangitis.