PURPOSE: To evaluate the usefulness of percutaneous transhepatic biliary drainage (PTBD) tract dilatation using a Nipro set. MATERIALS AND METHODS: We dilated 28 percutaneous biliary drainage tracts up to 18F ; 26 procedures involved PTBD, and two, cholecystostomy. A Nipro set was used for dilatation, the purposes of which were stone removal (n=18) and choledochoscopic biposy (n=10). For dilatation, local anesthesia was used in all cases. RESULTS: In all patients, tract dilatation was successful. In 21 of 28 cases, dilatation of the right PTBD tract was involved, and in five of 28, dilatation of the left tract. In two cases, tract dilatation was done in cholecystostomy tracts. Complications encountered were pain (n=17), bradycardia (n=2), hemobilia (n=2), bleeding (n=1)and fever (n=1). CONCLUSION: In choledocoscopy, tract dilatation using a Nipro set is safe and simple.