For fear of endophthalmitis and siderosis, ferrous intraocular foreign bodies are usually removed as soon as they are discovered; markedly reduced, siderotic ERG changes are considered permanent. We report a patient who presented with a chronically retained intravitreal foreign body and significant clinical as well as electrophysiologic signs of siderosis. Only 3 months after surgery, the ERG showed almost complete recovery. If siderosis is not present, adequate and regular follow-up examinations may in certain cases substitute for immediate removal of chronically retained intraocular foreign bodies.