In the last several decades, several acute and subacute disorders of the outer retina, pigment epithelium, and choroid have been described, primarily on the basis of their clinical features. These include central serous chorioretinopathy (CSC),¹⁰ birdshot chorioretinitis,³¹ multifocal evanescent white dot syndrome (MEWDS),²² acute zonal occult outer retinopathy (AZOOR),¹³ punctate inner choroidopathy (PIC),³⁶ multifocal choroiditis with panuveitis (MCP),⁸ serpiginous choroiditis,³² and acute multifocal posterior placoid pigment epitheliopathy (AMPPPE).¹¹ In many cases, these disorders exhibit features suggestive of an inflammatory or autoimmune etiology. As awareness of these disease entities has emerged from the clinical descriptions, with little understanding of their underlying causes, it has seldom been possible to differentiate between them with confidence.¹⁶ In some cases, there may also be overlap with syndromes that are defined in terms of retinal disturbances (e.g., acute macular neuroretinopathy) or in terms of the resulting visual disturbance (e.g., acute idiopathic blind spot enlargement syndrome).¹⁷ While it is not feasible here to fully reconcile the nosology of these overlapping conditions, this chapter will summarize the clinical and electrophysiological features of several of those conditions (central serous chorioretinopathy, birdshot chorioretinitis, multifocal evanescent white dot syndrome, and acute zonal occult outer retinopathy) in which electrophysiological studies may play a useful role.