The major neuroimaging modalities employed in the evaluation of patients with neurologic disorders include computed tomography (CT), magnetic resonance imaging (MRI), nuclear imaging, neurosonology, and endovascular procedures. In this dedicated volume of Seminars in Neurology, we will focus on CT, MRI, positron emission tomography (PET), and single photon emission computed tomography (SPECT) neuroimaging, including a brief review of their technical considerations and a broad consideration of their clinical applications.How does the need arise for Seminars in Neurology to review neuroimaging? First, there is no question that neuroimaging plays an increasingly central role in the diagnosis, therapeutic monitoring, and scientific investigation of a host of neurologic disorders. 1 Witness for example that the 2003 Nobel Prize in Medicine was awarded to the co-inventors of MRI, as evidence of how this technique has revolutionized the neuroscience field. 2 The role of neuroimaging continues to expand due to rapid advances in technology. 1 Second, neurologists are keenly interested in applying neuroimaging to their clinical practice and research investigations. [3][4][5][6] In 1996, a survey 3 of the members of the American Academy of Neurology (AAN) revealed that many neurologists relied on their own neuroimaging reading alone and a clear majority relied on a combination of their own and someone else's reading (58% for CT and 68% for MRI) to make clinician decisions. Less than 8% relied solely on someone else's CT or MRI interpretation. Nine years later, a survey 4 by the AAN showed a growing self-reliance by neurologists in the interpretation of MRI. In a 2002 international survey, 79% of neurologists stated that they made clinical decisions on stroke care based solely on their independent review of neuroimaging studies. 5 The importance of neuroimaging training for neurology residents has been stressed by the AAN 6 1 stated that residents in neurology must have adequate experience in neuroimaging that assures proficiency in CT, MRI, and neurosonology. 7 In 2008, the United Council for Neurologic Subspecialties, representing all of organized neurology in the United States, launched a new certification and accreditation pathway for neurologists in neuroimaging. 8 In this volume, the authors begin with brief overviews of the technologic aspects of MRI, PET, and SPECT. For MRI, this will include a discussion of the foundations behind functional, diffusion, perfusion, and spectroscopic MRI. A full consideration of neuroimaging physics, artifacts, hardware, and safety is beyond the scope of this volume. The authors then describe many of the neurologic conditions in which cranial and spinal imaging are applied in research and clinical settings in children and adults, including stroke, multiple sclerosis, degenerative conditions, dementia, tumors, toxic-metabolic disorders, infections, epilepsy, and hemorrhage/trauma. This volume concludes with a review of the current climate relating to neuroimaging practice.I am gratefu...