Evaluation of the nontraumatic acute abdomen with multidetector CT has long been accepted and validated as the reference standard in the acute setting. Dual-energy CT has emerged as a promising tool, with multiple clinical applications in abdominal imaging already demonstrated. With its ability to allow characterization of materials on the basis of their differential attenuation when imaged at two different energy levels, dual-energy CT can help identify the composition of internal body constituents. Therefore, it is possible to selectively identify iodine to assess the enhancement pattern of an organ, including the identification of hyperenhancement in cases of inflammatory processes, or ischemic changes secondary to vascular compromise. Quantification of iodine uptake with contrast material-enhanced dual-energy CT is also possible, and this quantification has been suggested to be useful in differentiating inflammatory from neoplastic conditions. Dual-energy CT can help determine the composition of gallstones and urolithiasis and can be used to accurately differentiate uric acid urinary calculi from non-uric acid urinary calculi. Moreover, dual-energy CT is capable of substantially reducing artifacts caused by metallic prostheses, to improve the imaging evaluation of abdominopelvic organs. The possibility of creating virtual nonenhanced images in the evaluation of acute aortic syndrome, gastrointestinal hemorrhage and ischemia, or pancreatic pathologic conditions substantially reduces the radiation dose delivered to the patient, by eliminating a true nonenhanced acquisition. Finally, by increasing the iodine conspicuity, contrast-enhanced dual-energy CT can render an area of free active extravasation or endoleak more visible, compared with conventional single-energy CT. This article reviews the basics of dual-energy CT and highlights its main clinical applications in evaluation of the nontraumatic acute abdomen. ©RSNA, 2019.