This study was designed to measure the concentration of ofloxacin in aqueous humor after topical, oral and intravenous administration in 50 patients undergoing cataract extraction. In Group I, ofloxacin 0.3% eyedrops were topically instilled ten times and the aqueous humor concentration was 2.73 +/- 0.88 mu g/ml. In Group 2, ofloxacin 0.3% eyedrops were topically instilled six times and the aqueous humor concentration was 0.84 +/- 0.61 mu g/ml. Aqueous humor concentration 12 hours after 200 mg oral dose in Group 3, was 0.38 +/- 0.12 mu g/ml. In Group 4, patients were given ofloxacin as a single intravenous 200 mg dose and the aqueous humor concentration 2 hours after the end of infusion was 0.45 +/- 0.11 mu g/ml. Concentrations were determined by high performance liquid chromatography (HPLC) with fluorescence detection.