The effect of inflammation on the intraocular penetration of ofloxacin was studied in 20 albino rabbits (New Zealand White). Inflammation was induced in the left eye by inoculation of a suspension of 10(9) CFU of heat-killed Staphyloccus epidermidis per 0.1 ml of saline solution (0.9%) in the midvitreous cavity. The other eye was kept as a control. Twenty-four hours following inoculation, ofloxacin was administered in the marginal ear vein at a dose of 15 mg/kg over 20 min with an infusion pump. Animals were sacrificed at different times up to 24 h following drug administration. Ofloxacin levels were determined in aqueous humor, vitreous humor, and serum by a bioassay. Inflammation was scored on the basis of perilimbal and corneal reactions and vitreoretinal statuses. Inflammation had a relevant effect on intraocular penetration of ofloxacin, with levels in the ocular fluids of the inflamed eye markedly exceeding the ones of the control eye. In the uninflamed eye, the levels were rapidly decaying below assay sensitivity and were no longer detectable at approximately 5 h following drug administration while they were still detectable in both ocular fluids of the inflamed eye at 24 h. Ofloxacin levels in the ocular fluids of the inflamed eye were superior to the MIC for several of the bacteria which commonly cause endophthalmitis, including Staphylococcus epidermidis, Staphylococcus aureus, most members of the family Enterobacteriaceae, Haemophilus influenzae, and strains of Pseudomonas aeruginosa.