This paper describes the concept and construction of an ERG-EOG apparatus which satisfies the requirements of clinical routine and which is realizable at a reasonable cost. The instrument comprises a ganzfeld stimulator (Ulbricht sphere), with a filter bank holding up to six filters, a flash lamp, and small stimulus lamps for the EOG. The responses are recorded binocularly. The electronic components are commercially available (high quality industrial electronics). The ERG may be recorded with the patient sitting or supine.