Because suture erosion after keratoplasty is an important risk factor for inflammation, infection, vascularization, and graft rejection, we aimed to delineate patient characteristics associated with these erosions. One hundred eyes of 97 consecutive patients who presented to our service with 10-0 nylon suture erosion after keratoplasty were selected for study. Patient age, preoperative diagnosis, duration from surgery, location and type of eroded suture, vascularity of recipient bed, contact lens or topical steroid use, and presence of infiltrate at the erosion site and subsequent culture results were tabulated. The average duration from keratoplasty to presentation was 33 (range 1-144) months. The locations of the eroded sutures were superior in 53%, nasal in 17%, temporal in 16%, and inferior in 14% of eyes (p < 0.005). Seventy-one percent of the eyes presented with broken sutures (an average 36 months postoperatively) and 29% with intact but loosened eroded sutures (an average 25 months postoperatively, p < 0.05). Sixty-nine percent of the eyes were being treated with topical steroids and presented 11 months earlier (29 months postoperatively) than did those not being treated with topical steroids (40 months postoperatively, p < 0.05). Eyes that had been subjected to keratoplasty for inflammatory conditions presented with suture erosion 10 months earlier than did those that had been subjected to keratoplasty for noninflammatory conditions (p = 0.09). Of the 10 eyes with a suture-related stromal infiltrate, one was culture-positive. Increased elapsed time from surgery, superior position of the suture, topical steroid use, and inflammatory ocular disorders are associated with suture erosions after penetrating keratoplasty.