The efficacy of eye drops and subconjunctival injections in the treatment of bacterial corneal ulcers for each of the following combinations were compared: cefazolin for staphylococcal ulcers, gentamicin for staphylococcal ulcers, and gentamicin for pseudomonal ulcers. Topical and subconjunctival therapy were equally effective in reducing the numbers of viable bacteria in experimental corneal ulcers. Subconjunctival injections produced high but transient peaks followed by persistent low troughs. In contrast, eye drops produced moderate but sustained concentrations throughout the treatment period. Under the conditions of this study, it appears that transient high peaks are not needed to eliminate bacteria effectively from a corneal ulcer. Since eye drops and subconjunctival injections are equally effective, other factors should determine the preferred route or routes of therapy.