Acute recurrent pancreatitis (ARP) results most commonly from alcohol abuse or gallstone disease. Initial evaluation fails to detect the cause of ARP in 10-30% of patients, and as a result the diagnosis of "idiopathic" ARP is given. In these patients, a more extensive evaluation including specialized labs, ERCP, endoscopic ultrasound, or magnetic resonance cholangiopancreatography typically leads to a diagnosis of microlithiasis, sphincter of Oddi dysfunction, or pancreas divisum. Less commonly, hereditary pancreatitis, cystic fibrosis, a choledochocele, annular pancreas, an anomalous pancreatobiliary junction, pancreatobiliary tumors, or chronic pancreatitis are diagnosed. Determining the etiology is important, as it helps to direct therapy, limits further unnecessary evaluation, and may improve a patient's long term prognosis.