Cytopathological examination After inclusion of the total number of patients, labels and marks on the smears will be removed and replaced by random numbers. Two non-consecutive random numbers from 1 to 1000 will be selected for each patient, one for the smear obtained with the G.I.U.M., the other for the smear obtained with the brush by JMD. Smears will be re-read by two cytopathologists blinded to the name of the patient, the technique of tissue sampling, previous diagnosis, as well as the relationship between the 2 random numbers for each pair of samples collected from the same patient (so avoiding interpretation of a sample obtained using one of the 2 techniques with the knowledge of the sample obtained from the same patient using the other technique). Indeed, their knowledge will be limited to the fact that a biliary stricture was identified at ERCP. Final diagnosis will be reached by agreement between the 2 cytopathologists. Specimens will be interpreted as normal, atypical (considered benign), highly atypical (suspicious for cancer), and malignant. Cell cellularity and single epithelial cell cellularity will be graded as absent, rare, moderate, or numerous. Finally, nuclear detail will be graded as poor, satisfactory, or excellent. Other data will be recorded as indicated in Table 1.