The visual evoked potential (VEP) is an electronic potential recorded from the visual cortex in response to a visual stimulus. It provides a means to examine the function of the visual pathway from the retina to the occipital cortex. The most common animals employed in VEP laboratory studies are rats. In this chapter, we describe the basic 'flash VEP' recording protocol in rodents and discuss the practical aspects of the preparation including anaesthesia methods, electrode configuration, stimulus design, dark adaptation, filter settings and signal sampling with the authors' personal experience. We also review the recent use of the VEP in laboratory researches in several optic nerve disease models, including glaucoma, ischemic optic neuropathy and optic neuritis.