ABSTRACT.Electrical signals generated in any biological system can travel to the surface by volume conduction. Near-field potentials are generated close to the recording electrode; far- field potentials are generated at a distance from the recording electrode. Biological electrical signals are often dipoles with a negative and a positive end. EEG and evoked potential studies may record one or both ends of the dipole, as either near-field or far-field potentials. The morphology and apparent polarity of recorded waveforms are determined in part by the orientation of the dipole, the direction of spread, and the derivation used for recording.