Every year, millions of CT scans are performed around the world for a wide variety of indications. Dual-energy CT (DECT), the focus of this chapter, is an emerging robust technique with sound technical foundation and multiple implementations, and is currently available for routine clinical use. In DECT, multiple X-ray spectra are utilized to characterize material-specific photon attenuation. This is a key advantage of DECT over conventional single-energy CT, and presents a radical departure from the conventional CT imaging paradigm. In this chapter, we describe the fundamental principles behind the DECT technology, and provide an overview of six different implementations of this type of scanner with comparisons of their relative pros and cons. Subsequently, we provide a discussion of practical issues related to DECT protocols and processing techniques from a clinical workflow point of view. We conclude the chapter by illustrating multiple neuroradiologic applications of this novel imaging technique, ranging from material characterization, beam hardening, and metal artifact reduction, to soft tissue contrast accentuation and contrast material quantification.