AIM: Topical glucocorticosteroids are administered to virtually every corneal transplant recipient, but irreversible immunological rejection remains the leading cause of graft failure. Ex vivo gene therapy of the donor cornea has been shown to modulate graft rejection in experimental models. The efficacy of a glucocorticosteroid-inducible promoter was assessed in controlling transgene expression following lentivirus-mediated gene transfer to ovine and human corneas. METHODS: A glucocorticosteroid response element (GRE5) was cloned into a lentiviral vector (LV-GRE-IL10) encoding the model transgene interleukin 10. Transgene expression by LV-GRE-IL10-transduced A549 cells, ovine corneas and human corneas cultured with or without dexamethasone was quantified by an IL10-specific enzyme-linked immunosorbent assay. RESULTS: IL10 levels were 30-40-fold higher in supernatants from LV-GRE-IL10-transduced A549 cells cultured with dexamethasone than in controls. Dexamethasone withdrawal resulted in restoration of baseline IL10 levels. Supernatants from LV-GRE-IL10-transduced ovine and human corneas cultured in dexamethasone contained nine to 10 times more IL10 than supernatants from transduced corneas cultured without dexamethasone. CONCLUSION: The GRE5 promoter in a lentiviral vector drove rapid, sustained and inducible transgene expression in both ovine and human corneas in the presence of dexamethasone. A steroid-inducible promoter may be useful for controlling transgene expression in gene-modified donor corneal allografts.