The different indications for penetrating keratoplasty are discussed on the basis of the clinical results of the past five years. Keratoconus is the most important group, followed by other corneal dystrophies, metaherpetic keratitis, graft failures and corneal scars. The results are very good in the first two groups, much less so in the last two. Eyes with repeated keratoplasty have a bad prognosis. One-half of the regrafts become cloudy. The most important postoperative complications, such as wound dehiscence, glaucoma, allograft reaction and anterior synechias are discussed.