Several growth factors have been evaluated for their effects on corneal wound healing but few studies have yet demonstrated an acceleration of endothelial repair in vivo. Mesodermal Growth Factor (MGF) was tested in vivo by making standardized freeze wounds in cat corneas and immediately injecting one of four concentrations of MGF in sterile phosphate buffered saline (PBS), or PBS alone, into the anterior chamber. Seven days later, the animals were sacrificed and the corneas excised and stained. Descemet's membrane and endothelium were dissected and mounted onto glass slides. The wound areas were photographed, measured and compared statistically. Those cats receiving the three lowest doses of MGF had significantly smaller wounds than controls (p less than 0.05).