Corneal buttons from two patients with failed epikeratoplasties requiring penetrating keratoplasty were examined by light and transmission electron microscopy. Penetrating keratoplasty was performed for lenticule scarring in the first case (adult aphakia) and inadequate best corrected visual acuity in the second case (keratoconus). Findings included decreased lenticule keratocytes and electron-dense, fibrillogranular material associated with either lenticule or recipient keratocytes in both corneas and defects in Bowman's layer in one cornea. In addition, light and electron microscopic evidence consistent with recipient keratocyte migration into the lenticule was demonstrated in one case. These findings were compared with three previous cases.