Aqueous and vitreous kinetics were studied after anterior subconjunctival injection of 100 mg of ceftriaxone sodium in phakic and aphakic rabbit eyes. Mean peak ceftriaxone concentrations (microgram per milliliter +/- SE, n = 3 to 5 rabbits per determination) were as follows: phakic eyes, 159.5 +/- 42 at one hour in aqueous humor and 25.3 +/- 6.6 at two hours in vitreous fluid; aphakic eyes, 105.1 +/- 20.5 at one hour in aqueous humor and 43.1 +/- 15.4 at one hour in vitreous humor. The ability of ceftriaxone to eliminate an incipient bacterial infection was also evaluated. Ten aphakic rabbits were challenged intravitreally with 700 colony-forming units of Staphylococcus aureus. Six of the ten immediately received subconjunctival injections of ceftriaxone sodium (100 mg). At 48 hours following the challenge, all four control eyes yielded greater than 5.6 X 10(5) colonies per milliliter. In the six eyes receiving ceftriaxone, five were sterile and one yielded 1.4 X 10(2) colonies per milliliter.