Objective To evaluate the effectiveness and safety of somatostatin and the analogue-octreotide in preventing post-ERCP pancreatitis. Methods We searched Cochrane Clinical Trial Register （Issue 1, April, 2004 ）, MEDLINE （1966- April, 2004）, EMBASE （1985- April, 2004）, CBM disc （1970- April, 2004） and The Clinical Trial Register of Chinese Evidence-Based Medicine Center and handsearched the related journals to identify Randomized Controlled Trials （RCT）of somatostatin and octreotide in post-endoscopic retrograde chnlangiopancreatography pancreatitis（PEP）prevention. Systematic review was conducted using the method recommended by The Cochrane Collaboration. Results Thirty-one trials involving 4 728 patients undergoing ERCP were included. Meta-analysis showed that the incidence of post-ERCP pancreatitis [ OR 0.33, 95% CI 0. 20 to 0. 54; P =0. 000 01 ; NNT =13] was significantly reduced by somatostatin. Octreotide could only reduce the incidence of hyperamylasemia [ OR 0. 54, 95% CI 0. 38 to 0. 77 ; P =0. 000 7 ]. The inci- dence of PEP, severe PEP and post-ERCP abdominal pain could not be reduced by octreotide. Conclusions Somatostatin can prevent post-ERCP pancreatitis. Four trials are of high quality in the 12 included studies and the results are consistent with the sensitive-analysis, so it is credible to some extent. However, existing evidence does not support that octreotide can reduce the incidence of PEP, so it is not recommended for this indication. Sensitive-analysis even showed that octreotide could increase the incidence of PEP. Therefore, whether it is necessary to carry out further clinical trials should be considered with caution.