We are conducting a controlled prospective multicentre randomized study to compare the double guide wire technique with the conventional method in two groups previously randomized after presenting a difficult selective biliary cannulation under the conventional method. The study is carried out in six public Hospitals from Spain. Assignation is concealed to both groups, and the expected study period is 18 months for a number of randomized patients equal or over 262 (statistical power of 90% with an α-error of 0.05, to detect a success rate of 74% in the group undergoing double guide wire technique against a success rate of 60% in the control group). The main outcome variables are successful selective biliary cannulation (primary outcome variable), number of attempts and morbimortality associated in both groups (secondary outcome variables).