Advances in imaging hardware for positron emission tomography and single-photon emission CT, coupled with a wide variety of radiopharmaceutical agents, have allowed these techniques to be used in the evaluation of neoplasm, stroke, epilepsy, and dementia. Cerebral perfusion agents continue to be the mainstay of single-photon emission CT imaging but, in addition to the evaluation of ischemia, it has seen an increasing role in the study of dementia, neuropsychiatric disorders, and seizures. Positron emission tomography scanning has had similar applications but it is playing a greater part in the evaluation of neoplasms, including primary gliomas and pituitary adenomas. Stable-xenon CT has shown value in the study of ischemia associated with meningitis, sickle cell disease, chronic subdural hematomas, and cerebral arteriovenous malformations. MR diffusion imaging shows promise in the evaluation of white matter pathology and some tumors.