The electronegative electroretinogram (ERG), also referred to as a negative ERG, is a very distinctive electrophysiological finding that has significant importance in not only establishing the correct diagnosis, but also localizing the source of the abnormality within the retina. An electronegative ERG has classically been defined as an ERG in which the a-wave amplitude is normal but the b-wave amplitude is severely subnormal, being smaller in amplitude than the a-wave. Within the past two decades, the term electronegative ERG has been expanded to include not only the classic definition, but also any ERG in which the b-wave is smaller than the a-wave, even when the a-wave itself is clearly subnormal. Moreover, although the term was initially applied only to the dark-adapted mixed rod-cone bright-flash ERG, the term has recently been used to describe a similar configuration for the light-adapted cone ERG.^34,72