This chapter provides an overview of electrophysiology and inflammatory disease. The information provided by electrophysiological assessment can have a significant effect on the diagnosis and management of the patient with retinal dysfunction related to inflammatory disease. The electroretinogram (ERG) is the mass electrical response of the retina elicited by luminance stimulation ERGs are recorded using corneal electrodes with stimuli delivered by a Ganzfeld bowel to enable uniform whole field illumination. The ERG is a mass response and is therefore not significantly affected when dysfunction is confined to small retinal areas. The pattern electroretinogram (PERG) is usually evoked by a reversing black and white checkerboard and is the response of central retina to an iso-luminant stimulus. It allows both a measure of central retinal function, and, because of its cellular origins, an evaluation of retinal ganglion cell function. Macular function is also assessed using multifocal electroretinography (mfERG) which, in addition, provides spatial information regarding central retinal cone system function. The clinical application of ERG is in birdshot chorioretinopathy (BCR) which is a chronic, usually bilateral, inflammatory disorder characterised by multiple discrete cream coloured areas of subretinal hypopigmentation, cystoid macular oedema (CMO), vitritis, and retinal vasculitis. The creamy white areas of depigmentation may not be seen in the early stages, and, when present may be confluent or may radiate outwards from the optic disc. As in BCR, the degree of ERG abnormality may be much greater than would be predicted by sometimes minor symptoms and/or signs. The exact aetiology of AZOOR (acute zonal occult outer retinopathy) is not fully understood, but it may be consequent upon inflammatory disorders such as multifocal inner choroiditis (MIC), punctuate inner choroidopathy (PIC), multiple evanescent white dot syndrome (MEWDS), acute macular neuroretinitis (AMN), etc. AZOOR has no specific abnormality in the area of retina responsible for the visual field loss. ICG angiography may reveal characteristic changes even when the fundus appearance has returned to normal. Electrophysiological assessment shows that retinal dysfunction is responsible for the visual field loss.