The primary neurologic application of event-related potentials (ERP) to date has been of relatively short-latency (less than 100-200 ms), stimulus-dependent components. These so-called exogenous components are used to evaluate the structural, and to a lesser extent, the functional integrity of primary afferent pathways. Another class of ERP, termed endogenous, and involving longer-latency (greater than 100 ms) stimulus-independent components has been utilized by psychologists and cognitive psychophysiologists in the measuring of neurocognitive processes. Although the experimental specification of these neurocognitial processes is still in its infancy, the empirical applications of endogenous ERP's offers considerable promise for objective non-invasive evaluations of cognitive functions now conducted only behaviorally. Initial neurocognitive ERP applications have focused on global mental status in dementia. A brief review is presented of experimental studies of some endogenous ERPs (mainly P300), their hypothesized underlying neurocognitive processes, and initial and potential clinical applications.