OBJECTIVE To assess the visual outcome after unilateral penetrating keratoplasty (PKP) in a heterogenous group of patients with unilateral corneal disease. METHODS A retrospective analysis of hospital records of patients who had undergone PKP at the Royal Victorian Eye and Ear Hospital, Melbourne, Australia, over a 10-year period, was performed. All cases with a history of corneal transplantation surgery in one eye and a best-corrected visual acuity (BCVA) more than or equal to 0.5 in the fellow eye with no corneal pathologic condition were included. Outcome measures included BCVA at 2 years, and overall graft survival. RESULTS Of the 498 grafts performed during the study period, 30 eyes (6%) met the inclusion criteria. The most common indications for PKP in the study group were bullous keratopathy (40%) and keratoconus (34%). The mean postoperative BCVA at 2 years (0.31 +/- 0.25; range, 0.033-1) was less than the mean BCVA of the fellow eye (0.77 +/- 0.20; range, 0.5-1) (P<0.00). Although there was a significant difference between the preoperative and postoperative BCVA (P<0.00), only 22% of patients could attain BCVA of more than or equal to 0.5. The major complications encountered were graft rejection (40%) and secondary graft failure (20%). CONCLUSIONS Unilateral PKP is most commonly performed to treat bullous keratopathy and keratoconus in Australia and may be associated with suboptimal visual outcome as compared to the normal fellow eye.