BACKGROUND: Small-sized tumors sited closer than 15 mm to the central bile ducts cannot be destroyed by radiofrequency (RF) because the resulting heating causes destruction and stenosis of the bile ducts. STUDY DESIGN: Thirteen patients underwent intraoperative RF to treat tumors closer than 6 mm to a central bile duct. Stenosis prevention was achieved by cooling the main bile duct(s) (right, left, or both) with a 4 degrees C saline solution quickly infused by a catheter introduced inside the bile duct through a choledochotomy. Median followup after cooling was 19.7 months (range 6 to 42 months). RESULTS: There was no mortality and no RF-related morbidity. Twelve patients (92.3%) did not present any biliary stenosis. In one patient (7.7%) biliary stenosis was detected 6 months after RF. The patient was cirrhotic but did not require any treatment. One of the 13 patients had a local recurrence. CONCLUSIONS: The intraoperative cooling of central bile ducts prevents biliary stenosis efficiently when using RF to destroy tumors closer than 5 mm to the bile duct. This new technique decreases the contraindications for the use of RF and allows more patients to be treated with RF with curative intent.