Purpose: To characterize the clinical and histologic features of primary graft failure after Descemet's stripping and automated endothelial keratoplasty (DSAEK). Design: Retrospective observational case series. Participants: Sixteen cases of DSAEK graft failure from 15 patients, all with detailed histologic examination of failed graft tissue. Methods: Hematoxylin-eosin, periodic acid-Schiff staining, and light microscopy were used to examine the failed DSAEK graft tissue from all patients. Main Outcome Measures: Examination of specimens for corneal endothelial cell viability and host-donor interface characteristics. Results: Clinical history revealed that 88% (14/16) of studied DSAEK grafts detached before failure, and pathologic examination found that 75% (12/16) of failed grafts had atrophic corneal endothelium. Examples of residual host Descemet's membrane in the graft site and improper donor trephination were also identified. Conclusions: Marked loss of the corneal endothelium is the prominent feature of primary DSAEK graft failure. Examples of surgical features, such as incomplete Descemet's stripping and residual full-thickness cornea with a DSAEK graft, are shown. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references. Ophthalmology 2009; 116:609-614 (C) 2009 by the American Academy of Ophthalmology.