Some patients with acute cholecystitis may have symptoms suggestive of an abscess or other intra-abdominal inflammation and, therefore, may be referred for a CT of the abdomen. This report reviews the pathophysiology, clinical presentation, and CT findings of acute cholecystitis (gallstones, wall thickening, distention, pericholecystic fluid, and pericholecystic stranding). Pitfalls and complications of the diagnosis are discussed. Those scenarios where CT may prove superior to ultrasound or hepatobiliary scintigraphy are highlighted.