Selected 240 cases obstructive jaundice. 120 cases calcular obstruction and 120 cases with malignant obstruction were studied of idenfication of the main causes of post ER.C.P. infective complications. The clinical, laboratory and endoscopic findings are discussed. It as found that the most important infective complications after E.R.C.B are biliary bacteremia, cholangitis, pancreatitis and septicemia, and the most important predisposing factors for these complications are inadequate instruments sterilization, calcular biliary obstruction or stricture, incomplete drainage of the biliary channels, the occurrence of mucosal lesions during the procedure, or overfilling of the biliary channels during the procedure and any cause of decreased patient immunity. It was found that intravenous injection of a suitable antibiotic gives the best results for prevention and control of these complications rather than the intraductal injection or washing only without antibiotic, somatostain proved to be of no benefit in that respect in our study. Thus we recommend I.V injection of a suitable antibiotics in these cases.