Endoscopic retrograde cholangio-pancreatography belongs to the diagnostical equipment of gallduct obstruction and obturation. ERCP is indicated if any doubts arise with the usual clinical diagnostic methods, laboratory, or x-ray studies. This paper presents the technique of ERCP and the several steps in its operation: pylorus passage, description and evaluation of the papilla of Vater and insertion of the papilla. Daily practice and patience produce successful work without complications. Rate of complication in 604 ERCP procedures = 2%. No lethal outcome was observed.