OBJECTIVE To investigate whether 193-nm excimer laser photorefractive keratectomy for the correction of myopia can determine in vivo changes in the human corneal endothelium 3 and 12 months after surgery. METHODS Contact wide-field specular biomicroscopy of the central corneal endothelium was performed on 76 eyes of 61 patients (aged 20 to 49 years; mean, 29.7 years) who underwent photorefractive keratectomy for the correction of myopia ranging between -1.75 and -13.50 diopters (mean, -6.60 D). The maximum estimated central depth of the photoablation was 113 microns. Photomicrographs of the endothelium taken before surgery were processed by means of computer-assisted morphometric analysis and compared with those obtained 3 and 12 months after surgery. RESULTS The mean (+/- SD) cell density was 2657 +/- 298 cells/mm2 preoperatively, 2672 +/- 286 cells/mm2 after 3 months (P = .670), and 2656 +/- 289 cells/mm2 after 1 year (P = .982). The mean (+/- SD) coefficient of cell area variation was 30.27% +/- 5.99% preoperatively, 28.25% +/- 5.21% after 3 months (P = .032), and 26.35% +/- 5.29% after 1 year (P = .001). The mean (+/- SD) percentage of hexagonal cells was 63.82% +/- 9.94% preoperatively, 64.02% +/- 10.53% after 3 months (P = .806), and 67.19% +/- 9.14% after 1 year (P = .025). CONCLUSIONS Photorefractive keratectomy caused no damage to the corneal endothelium. Postoperative improvements of the coefficient cell area variation and the percentage of hexagonal cell values may be related to corneal metabolic modifications or discontinuance of contact lens use after surgery.