This study reports an open randomised controlled trial of cyclical antibiotics and ursodeoxycholic acid in prevention of plastic biliary stent occlusion. Seventy patients with malignant distal bile duct obstruction were randomised to either active treatment with cyclical antibiotics (ampicillin, metronidazole, ciprofloxacin) and ursodeoxycholic acid or no treatment after successful stent insertion. The two groups were well matched. The follow up was complete with stent occlusion or death being the end points. There was no difference in the incidence of stent occlusion between the two groups and the overall survival was similar. In conclusion, this study did not show any benefit of treatment with antibiotics and ursodeoxycholic acid in prolonging stent patency or improving survival.