Protocol design and management policy Eligible patients will have tissue sampling performed using both techniques, the first technique used being randomly assigned and immediately followed by the other one. Randomization will be performed by opening an opaque sealed envelope numbered according to a table of random numbers with blocks of 6 patients; each center will receive a pack of 24 numbered envelopes (made by an investigation nurse). A listing of all patients with a biliary stricture diagnosed at ERCP will be maintained (name, surname, date of birth, and date of examination), and reason for non inclusion will be stated.