The effects of growth factors on re-epithelialization of wounded human and bovine corneas were studied in a simple organ culture system. Excisional trephine and epithelial scrape wounds were created on bovine and human corneo-scleral rings in which the endothelial corneal concavity was then filled with an agar-collagen mixture. Organ culture was undertaken at 37 degrees C in a humidified 5% CO2 incubator with serum-free Medium 199 maintained at the level of the conjunctival epithelium. Rates of reepithelialization in response to addition of exogenous epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and transforming growth factor type beta 1 (TGF-beta 1) were assessed by image analysis. Corneal cultures could be maintained for up to 3 weeks without significant stromal oedema or keratocyte deterioration and with little loss of epithelial architecture. Following wounding the cornea reepithelialized in a similar fashion to that observed in vivo i.e. a lag phase followed by migration/proliferation and the reformation of an intact multilayered epithelium. EGF accelerated, basic FGF had no effect on, and TGF-beta 1 inhibited the rate of corneal re-epithelialization. Our organ culture model maintains corneal integrity and provides a practical system in which to study factors that modulate corneal reepithelialization following wounding.