Purpose: To investigate whether use of same-size donor and recipient trephines reduced myopia after penetrating keratoplasty for keratoconus. Design: Retrospective cohort study. Participants: Eight hundred seventy-eight first grafts for keratoconus were reported to UK Transplant between April 1999 and December 2003. There were 234 and 644 grafts in the same-size and oversize donor trephine groups, respectively. At 1 year, mean spherical equivalent (SE) data were available for 116 eyes (50%) and 295 eyes (46%) in the same-size and oversize groups. At 2 years, mean SE data were available for 64 eyes (27%) and 148 eyes (23%) in the same-size and oversize groups. Methods: Logistic regression and univariate analysis of follow-up data submitted to UK Transplant. Main Outcome Measures: At 1 and 2 years postoperatively, mean SE, magnitude of the cylindrical component of the refraction, postoperative uncorrected visual acuity (VA), postoperative best-corrected VA, and postoperative complications were recorded. Results: The mean SEs for the same-size and oversize donor trephine groups, respectively, were -1.45 diopters (D) and -1.41 D at 1 year (P = 0.6) and -1.74 D and -2.19 D at 2 years postoperatively (P = 0.3). Although there were no differences in graft survival between the groups at 1 and 2 years, there was a higher incidence of postoperative wound leaks in the same-size group (P = 0.03). Conclusion: Use of same-size donor and recipient trephines did not reduce myopia and was associated with an increased risk of postoperative complications.