Radiotracer imaging methods such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are well suited to provide information about the functional, metabolic, and molecular status of tissues and organs. Brain SPECT has a well-established role for a number of clinical indications. Cerebral perfusion studies are used in the evaluation of dementias, epilepsy, cerebrovascular disease, trauma, brain death, and to assist with neuropsychiatric evaluation. Brain function is evaluated at baseline, before and after pharmacotherapy or psychotherapy, and following a number of activation tasks to examine a large number of psychiatric conditions. The integration of SPECT and CT in a single imaging device facilitates anatomical localization of the radiopharmaceutical to differentiate physiological uptake from that associated with disease. SPECT and SPECT/CT is continuing to evolve with the introduction of new technologies that have the potential to improve performance beyond that possible with Anger's pioneering approach.