In a retrospective study we evaluated 49 consecutive penetrating keratoplasties for herpes simplex keratitis. Mean follow-up was 44.2 months. Survival analysis with Kaplan-Meier curve showed an overall survival rate (clear graft) of 88% at one year, 76% at two years and 72% at four years postoperatively. Survival analysis showed a recurrence-free survival rate of 72% at one year, 59% at two years and 51% at four years postoperatively. Of the 13 non-primary graft failures, 9 happened in eyes with an HSV recurrence. Recurrence of HSV infection occurred in 18 (39%) eyes at an average of 12.6 months after surgery (range 0.3-46). Five (28%) of the recurrences occurred within two months after the start of steroid treatment for rejection. Nine (50%) of the recurrences cases resulted in a clouded graft at the end of follow-up. 73% of the eyes with a clear graft had a VA of 0.25 or better. We conclude from these data that a recurrence of a herpetic infection following corneal transplantation is the main reason for graft failure in this group.