A total of 16/206 eyes in 14/186 patients developed irreversible immune reactions. 15 of the rejected eyes belonged to the 'classical' risk groups, i.e. systemic immune disorders (3/3), metaherpetic keratitis (6/41), pseudophakic bullous keratopathy with inflammation (2/6), non herpetic keratitis with vessel invasion (1/23) and 3 regrafts not included in these groups (a total of 7/31 regrafted eyes rejected). Only 1 rejection occurred in the low-risk groups: an aphakic eye with bullous keratopathy. Histopathological examination revealed that discs which later developed irreversible immune reactions had invariably been grafted in eyes which had vascular invasion and/or inflammation of the recipient cornea. In all, 55/206 eyes ended up with opaque grafts, i.e. irreversible immune reactions were responsible for about one third to one-quarter of the graft failures in the present material. The irreversible immune reactions in the material must be considered 'minimum values', since possible abortive, torpid immune reactions may have escaped recording.