To determine whether the effect of fibronectin on corneal epithelial healing occurs in eyes affected by diabetes, the effect of fibronectin on the rates at which corneal epithelial wounds healed was compared in diabetic and normal rats. Streptozotocin was used to induce diabetes in rats. Two weeks after treatment, the whole corneal epithelium of diabetic and untreated rats was debrided. Fibronectin eye drops, at concentrations ranging from 0-01 to 1 mg ml-1, were given six times a day for three days, starting immediately after debridement. The area of the corneal epithelial wound was measured every 12 hr. Although the healing process was similar in normal and diabetic rats, the healing rate in diabetic rats was slower than that in normal controls after the 12 hr immediately following debridement. In both diabetic and normal rats, fibronectin eye drops reduced the wound area in a dose-dependent manner. The fibronectin dose of 1 mg ml-1 reduced the wound area significantly, compared with control eyes treated with phosphate-buffered saline. These results demonstrated that fibronectin facilitates corneal epithelial wound healing in diabetic rats.