Potentials that do not conform to an expected electrical field generated by the brain characterize an extracerebral source or artifact. Artifact is present in virtually every EEG. It is an essential component for routine visual analysis, yet it may beguile the interpreter into falsely identifying waveforms that simulate epileptiform discharges (ED). The principal importance of artifact is represented by the frequency of its occurrence in contrast to the limited frequency of normal variants that may imitate pathologic ED. Continuous EEG monitoring has uncovered newly identified artifacts unique to prolonged recording. The combined use of video and EEG has revolutionized our ability to distinguish cerebral and extracerebral influences through behavioral correlation that is time-locked to the electrophysiologic features that are present on EEG. Guidelines exist to ensure minimal standards of recording. Precise definitions are present for ED. Still, the ability to distinguish artifact from pathologic ED requires a human element that is to provide the essential identification of an abnormal EEG. The ramification of a misinterpreted record carries an acute risk of treatment and long-term consequences for diagnosis-related harm.