The effect that topically administered cyclosporine A (CsA) dissolved in olive oil has on corneal epithelial permeability was determined by fluorophotometry. Twentysix healthy volunteers, who had no ocular or general disease and were not receiving any topical or systemic treatments, were studied. A Fluorotron Master fluorophotometer was used. Measurements were taken before and 45 min after the instillation of 40 μl of a 2% aqueous solution of sodium fluorescein without preservatives. Basal corneal epithelial permeability, as well as the permeability 24 h after the instillation of 2% CsA-olive oil and of the solvent alone, were calculated. Under sterile conditions, the Sandimmun oral solution (Sandoz, Basel, Switzerland) was used to prepare the topical 2% CsA. Immediately after the 2% CsA-olive oil or the solvent alone were instilled, the volunteers complained of itching for ~1 h and developed punctate keratopathy, which improved the next day. Epithelial permeability 24 h after instillation of 2% CsA-olive oil increased 7.03 times (p < 0.001), and that of the solvent alone increased 6.68 times (p < 0.001). No differences in corneal permeability were found between CsA-olive oil and the vehicle (p = 0.651). We concluded that the olive oil used to dissolve CsA is responsible for the increased corneal epithelial permeability.