Corticosteroids are by far the most frequently used agents to treat ocular inflammation. When administered topically to the eye, different derivatives of the same corticosteroid base are not equivalent in their antiinflammatory properties. A change in the derivative of a corticosteroid base alters its behavior as an antiinflammatory agent. To date, the acetate derivative of each corticosteroid base studied has been the most effective, and among commercially available ophthalmic formulations, 1.0 percent prednisolone acetate is the drug of choice for maximal antiinflammatory effect. Hourly instillation produces a greater, more rapid reduction of corneal inflammation than does instillation of the drug every 4 hours, while instillation at 15-minute intervals results in an even greater therapeutic effect. Topical delivery of five doses of 1.0 percent prednisolone acetate at 1-minute intervals each hour results in an antiinflammatory effect comparable to that achieved by instillation every 15 minutes. Topical instillation of a corticosteroid produces a greater reduction in inflammatory cells invading the cornea than does periocular injection of a steroid. Administration of corticosteroids concurrently by topical and subconjunctival routes produces an additive antiinflammatory effect. Addition of a topically applied corticosteroid to an effective topical antibiotic regimen containing a bactericidal agent does not enhance bacterial replication in the cornea if the corticosteroid is not instilled more frequently than the antibiotic. Corticosteroids enhance viral proliferation and are contraindicated in active epithelial herpetic keratitis. Many instances of stromal herpetic keratitis appear to be a toxic or immune response to incomplete, nonreplicating viral particles rather than alteration of tissue by multiplying live virus, and the judicious use of corticosteroids is advocated along with an antiviral antimetabolite. Because control of replicating fungal organisms by specific antifungal agents is often difficult to achieve, corticosteroids should not be used in the treatment of mycotic keratitis.