We have studied in rabbits the effect of subconjunctivally injected hydrocortisone on the polymorphonuclear leucocyte invasion of corneal wounds at different times after an injury. One group of rabbits was treated with the steroid (hydrocortisone group) and the other not (control group). After making nonpenetrating trephine incisions on the cornea we obtained cellular samples by the impression technique at a given postoperative period (2, 4, or 6 hours), and then the animal was killed. The cornea was processed for histological study of the infiltrating cells. At any postoperative period the number of polymorphonuclear leucocytes in the corneal wounds of the hydrocortisone group was significantly less than the number in the identical wounds of the control group (p less than 0.01 to 0.001).