PURPOSE: To compare the bacteriologic and clinical efficacy of gatifloxacin and ciprofloxacin for the treatment of bacterial keratitis. DESIGN: Prospective, randomized clinical trial. METHODS: A total of 104 eyes of 104 patients with bacterial keratitis seen at a tertiary eye-care center were randomized to treatment with gatifloxacin 0.3%eyedrops (GAT group, 50 eyes) or ciprofloxacin 0.3%eyedrops (CIP group, 54 eyes). Patients and the treating physician were masked to the antibiotic being used. Main outcome measure studied was healing of the ulcer. Patients lost to follow-up before complete healing were excluded from further analysis. RESULTS: A significantly higher proportion of ulcers in the GAT group exhibited complete healing compared with those in the CIP group (39 eyes 95.1% vs 38 80.9% ; P=.042). Gatifloxacin demonstrated a significantly better action than ciprofloxacin against gram-positive cocci in vitro (P < .001), and the percentage of ulcers caused by these pathogens that healed in the GAT group was significantly better than in the CIP group (P=.009). Mean time taken for healing of ulcer and the efficacy against gram-negative bacteria did not significantly differ between the two groups. CONCLUSIONS: Gatifloxacin had a significantly better action against gram-positive cocci both in vitro and in vivo when compared with ciprofloxacin. In view of these organisms being the leading cause of keratitis worldwide, gatifloxacin may be a preferred alternative to ciprofloxacin as the first-line monotherapy in bacterial keratitis. PURPOSE: To compare the bacteriologic and clinical efficacy of gatifloxacin and ciprofloxacin for the treatment of bacterial keratitis. METHODS: A prospective, randomized clinical trial. METHODS: A total of 104 eyes of 104 patients with bacterial keratitis seen at a tertiary eye-care center were Patients and the treating physician were masked to the antibiotic being used. Main outcome measure was washes of the ulcer (CIP group, 54 eyes). randomized to treatment with gatifloxacin 0.3% eyedrops (GAT group, 50 eyes) or ciprofloxacin 0.3% eyedrops . Patients lost to follow-up before complete healing were excluded from further analysis. RESULTS: A significant higher proportion of ulcers in the GAT group exhibited complete healing compared with those in the CIP group (39 eyes 95.1% vs 38 80.9%; P = .042). Gatifloxacin demonstrated a significantly better action than ciprofloxacin against gram-positive cocci in vitro (P <.001), and the percentage of ulcers caused by these pathogens that h ealed in the GAT group was significantly better than in the CIP group (P = .009). Mean time taken for healing of ulcer and the efficacy against gram-negative bacteria did not significantly differ between the two groups. CONCLUSIONS: Gatifloxacin had significantly better action against gram-positive cocci both in vitro and in vivo when compared with ciprofloxacin. In view of these organisms being the leading cause of keratitis worldwide, gatifloxacin may be a preferred alternative to ciprofloxacin as the first-line monotherapy in bacterial keratitis.