BACKGROUND/AIMS: White bile is colorless, translucent fluid found occasionally in malignant bile duct obstruction (MBO). Little information is available on the cause and effect of white bile. The aim of this study was to determine the frequency and clinical significance of white bile in MBO. METHODS: Bile was aspirated during endoscopic retrograde cholangiopancreatography in consecutive patients with MBO. White bile was defined as bile bilirubin <1.5 mg/dL and yellow bile was defined as bile bilirubin >or=1.5 mg/dL in the bile. Two groups were compared prospectively for the duration of jaundice, itching, cholangitis, level of obstruction, and decremental rate of bilirubin after the insertion of 7 Fr endoscopic nasobiliary drainage until the insertion of metal stent or 10 Fr plastic stent. RESULTS: Among 60 patients with MBO, 16 (26.7%) had white bile. WBC count in blood was higher (9,456/mm3 vs. 7,400/mm3, p=0.029) and cholangitis was more common (11/16 vs. 7/44, p=0.000) in white than yellow bile group. Proximal portion of MBO had no communication with GB in 9/16 patients with white bile group and 17/44 patients with yellow bile group (p>0.05). Mean survival of the inoperable 35 patients was 242 days in yellow bile and 227 days in white bile group (p>0.05). CONCLUSIONS: White bile in MBO was not rare and was associated with cholangitis. Gallbladder did not seem to play a role in the formation of white bile. Further study for the pathogenesis and prognosis of white bile in MBO will be necessary.