The effect of prednisolone on tobramycin and carbenicillin therapy for experimentally induced Pseudomonas keratitis was evaluated. Results were assessed quantitatively by determining the number of bacteria that survived in the cornea. Simultaneous administration of prednisolone did not adversely alter results of treatment with carbenicillin or tobramycin. In another trial, pretreatment with prednisolone for 48 hours before antibiotic therapy was begun did not change significantly the results of therapy with intramuscular tobramycin or carbenicillin. We conclude that corticosteroid therapy does not affect adversely results of antibiotic therapy with tobramycin or carbenicillin in this experimental model.