A middle-aged man was admitted to the ED because of nausea and vomiting, abdominal distention and fainting. A blood analysis revealed high levels of serum amylase and lipase, confirming a diagnosis of acute pancreatitis. The history showed that the patient had self-administered a single dose of pegylated interferon alfa-2b and ribavirin daily for 7 days for chronic hepatitis C. The medications were stopped and his condition gradually improved. In agreement with the literature and the Naranjo algorythm result, pegylated interferon alfa-2b is associated with acute pancreatitis. Identification of a few signs and symptoms is the first 'signal' in preventing a serious drug-induced adverse event.