Fibronectin (FN) has been detected at the site of corneal wounds. To investigate whether FN is supplied by the cornea itself or by extracorneal sources, we cultured small blocks of rabbit cornea in vitro with and without autologous serum (5%). The sliding rate of epithelial cells was determined and localization of FN in the corneal block examined by indirect immunofluorescent microscopy. Epithelial cells slid more rapidly in the presence of serum and covered most of the stromal surface in about 24 hours. FN was detected at the surface edge of the cut stroma shortly after culturing began. During epithelial cell sliding, FN-specific fluorescence was noted beneath the migrating cells. The location of FN was essentially the same in cultures with and without autologous serum. These results suggest that FN might be supplied by the cornea itself and that it may play a role in epithelial cell sliding.