BACKGROUND: Pancreatitis is the most common major complication of endoscopic retrograde cholangiopancreatography (ERCP). Recent studies have suggested that obesity may serve as a prognostic indicator of poor outcome in non-ERCP-induced acute pancreatitis. However, to our knowledge, no one has ever investigated the potential association of obesity and ERCP-induced pancreatitis. Thus, the purpose of our study was to determine whether obesity conferred an increased risk and/or more severe course of post-ERCP pancreatitis. METHODS: A 160 variable database was prospectively collected by a defined protocol on patients undergoing diagnostic or therapeutic ERCP at 15 centers in the Midwest Pancreaticobiliary Group and participating in a randomized controlled study, evaluating whether prophylactic corticosteroids reduces the incidence of post-ERCP pancreatitis. Body mass indices (BMIs) were available on 964 of the 1115 patients from the original study. A BMI ≥ 30 kg/m was defined as obese (World Health Organization) and used as a cutoff point in this study. BMIs were analyzed in a retrospective fashion to determine whether obesity confers an increased risk and/or more severe course of post-ERCP pancreatitis. Data were collected before the ERCP, at the time of procedure, and 24 to 72 hours after discharge. Standardized criteria were used to diagnose and grade the severity of postprocedure pancreatitis. RESULTS: Nine hundred sixty four patients were enrolled in the study. Pancreatitis occurred in 149 patients (15.5%) and was graded as mild in 101 (67.8%), moderate in 42 (28.2%), and severe in 6 (4.0%). The patients were categorized by BMI (kg/m) using the following breakdowns: BMI <20, 20 to <25, 25 to <30, and ≥ 30, as well as BMI <30 or ≥ 30. The groups were similar with respect to the patient and procedure risk factors for post-ERCP pancreatitis except the group with BMI ≥ 30 had a higher frequency of females, were younger, had less frequent chronic pancreatitis, a lower number of pancreatic duct injections, and fewer patients received more than 2 pancreatic duct injections. Of the patients with a BMI <30, 119 (16.4%) developed post-ERCP pancreatitis compared with 30 (12.5%) of those with a BMI ≥ 30 (P=0.14). There was no association between the presence of obesity and the severity of pancreatitis (P=0.74). Patients with a BMI <20, 20 to <25, 25 to <30, and ≥ 30 had a similar incidence of post-ERCP pancreatitis. CONCLUSIONS: Obesity did not seem to confer an increased risk for ERCP-induced pancreatitis. A statistically significant association between obesity and the severity of ERCP-induced pancreatitis was not apparent.