The infection following endoscopic retrograde cholangiopancreatography (ERCP) is one of the most severe complications. The aim of the present study was to assess the prevalence and the prognosis of this complication, to look for the risk factors and to define bacterial ecology in order to put forward the most appropriate antibiotherapy. Two thousand and ten patients were included in this study. Among these, 51 (2.5%) had a septic complication following ERCP. Endoscopy biliary drainage was complete in 24 cases, incomplete in 19 and lacking in 8. Transhepatic biliary drainage was carried out in 17 cases. Sixteen patients (31%) with tumor obstructions died within 30 days after ERCP. Four risk factors were isolated when comparing infected patients with other patients: the completeness of biliary obstruction (90 vs 48%, P < 0.001); multiple cannulation attempts (1.76 +/- 1.12 vs 1.25 +/- 0.70, P < 0.001); the malignant nature of the obstruction (80 vs 23%, P < 0.002) and the lack of satisfactory drainage following endoscopy (53 vs 23%, P = 0.009). Pseudomonas aeruginosa was the most frequently isolated species, both from blood cultures (30%) and bile samples (23%). The preventive therapy of septic complications following ERCP must include strict rules concerning the disinfection of endoscopic material.(ABSTRACT TRUNCATED AT 250 WORDS)