Recent advances in computer technology make it relatively easy to generate color images representing the electrophysiologic activity of the brain. Because of the visual appeal of the images, and their similarity to computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans, there has been wide interest in these methods. Thorough understanding of these techniques is necessary to appreciate their strengths and limitations, and their proper application. This article explains the types of studies that are usually done, compares these methods with other imaging techniques, outlines their limitations, summarizes the literature on their use in psychiatry, and describes clinical situations in which these tests may be useful. This information will help the reader interpret clinical reports and research studies that employ these methods, evaluate representations made by commercial vendors of imaging systems, and understand the role these tests can play in his or her daily clinical practice.