Insights into how the nervous system functions have often sprung from knowledge of the localization of nervous system diseases. Indeed, the recent rebirth of behavioral neurology has been sparked by new insights into the topography of higher cortical functions. Yet, the localization of disease affecting the peripheral nervous system is simply assumed to be a by-product of the beginning course in gross anatomy! Indeed, the anatomic sophistication laid out by Sunderland and reflected in the daily practice of electromyography might cause doubt as to the need for further inquiry into the problem of localization of disease within peripheral nervous system. There are, however, numerous problems in clinical practice that do not yield to the traditional root-plexus-nerve analysis of localization.