Radioactive carbon-labeled penicillin G, chloramphenicol, or gentamicin were injected subconjunctivally into rabbit eyes. The distribution of antibiotics throughout the cornea was determined in relation to the injection site; aqueous humor levels were also measured. For chloramphenicol, the highest drug concentrations in the cornea were adjacent to the injection site; levels decreased as the distance from the injection site increased. For penicillin G and gentamicin, highest corneal levels were adjacent to the injection site. Levels were lowest in the central cornea but increased in the peripheral cornea, 180 degrees opposite the injection site. For all antibiotics, therapeutic levels were reached throughout the cornea irrespective of the injection site. Corneal values for all drugs were consistently higher than aqueous humor values. These results suggest that in the treatment of corneal ulcers the choice of subconjunctival injection site is not important.