This article discusses the relevance of quantitative EEG (QEEG) and live z-score training (LZT) to the field of mental health in general, and to neurofeedback in particular. We examine what practitioners might learn about clients when QEEG is used for assessment, and the relevance of LZT as a treatment modality. Clinicians can benefit from viewing the brain as a dynamic system, and this point of view can provide a foundation for QEEG and LZT. This approach emphasizes understanding the value of brain activation as a basis for observed symptoms and behaviors. Of paramount importance are localization and frequency information, as well as connectivity metrics. The brain can be viewed as a complex self-controlled system operating with various identifiable networks and frequencies that, when dysregulated, produce what we commonly refer to as “disorders.”