Acute pancreatitis (AP) is a common disease. In Finland, the most common etiological factors are alcohol abuse and biliary stone disease. Often the etiology of AP is multifactorial. AP may also occur as a complication after ERCP, pancreatic operation or ultrasound guided biopsy. It is important to find out the etiological factors to be able to prevent a recurrence of AP. It is estimated that only 5 - 10% of AP-cases should be declared as idiopathic. Anamnesis of alcohol consumption, medication, family history, injuries, and disease history should reveal many of the risk factors. The initial radiological imaging is ultrasound, which can be repeated to increase the sensitivity for detecting gallstones as the etiological factor. In certain cases MRCP, computed tomography or endoscopic ultrasound are needed.