Elevated carbohydrate antigen 19-9 (CA19-9) beyond 1000 U/L occurs in nonneoplastic conditions which is causing questioning of the use of CA19-9 as a marker for screening. We report a case where a 51-year-old male with Mirrizi Syndrome (MS) presented with markedly increased CA19-9 level (4,618 U/mL). MS is a rare complication characterized by compression of the common bile or hepatic duct caused by an impacted gallstone in the cystic duct or neck of the gallbladder. Biliary epithelial cells secrete CA19-9: it is hypothesized that increased proliferation of such cells caused by inflammation leads to increased secretion. CA19-9 should not be used as a diagnostic tool, but rather for surveillance.