The second part of this study deals primarily with the technical aspects of electroretinography. A custom made dark chamber for the patient is presented. The requirements for an optical stimulator are discussed in detail and the recording instrumentation--electrodes, amplifiers, averager, digitalizer--are presented. The display of the signals on a monitor and plotter concludes this technical description. The remainder of part 2 is devoted to the many factors influencing the recording of an ERG, notably pupillary diameter, anesthesia, oxygen and glucose supply to the animal, body temperature of the patient, its intraocular pressure and level of retinal adaptation, and finally the age of the patient. On the technical side the intensity, wavelength and frequency of stimulation play an important role.