It is evident that penicillin F did not cause any damage to the retina or other parts of the interior of the eye when 1,000 units was introduced. Penicillin X was well tolerated in the dose of 2,000 units. Circumscribed lesions of the retina, as observed with the preparation of penicillin G used in this series, were absent. When the dose of penicillin X was increased to 5,000 units, there was a localized area of injury in the neuroepithelium in 1 of 4 eyes. The retina was unchanged after injections of 2,000 units of commercial crystalline sodiumpenicillin.