ABSTRACT.The recording of bioelectric activity associated with physiological events is fundamental to electrophysiology. Clinical use of electroneurodignostics requires that electrodes be applied to the skin to view underlying neuronal events. Much emphasis has been placed on understanding the polygraphs, EEG instruments, and evoked potential equipment that make the measurements. The events that occur between the electrode and the neuronal events are also part of the recording. The millivolt electrical events in the cerebral cortex become microvolt signals on the EEG. EEG signals often contain interference or artifacts generated by the electrodes. Understanding of the electrodes, the skin surface, and the junction between them is essential to intelligent electrode application and troubleshooting.