To assess the clinical efficacy of cultivated oral mucosal epithelial transplantation (COMET) for the treatment of persistent epithelial defect (PED).We treated 10 eyes of nine patients with PED (Stevens-Johnson syndrome: three eyes; thermal/chemical injury: five eyes; ocular cicatricial pemphigoid: two eyes) with COMET at Kyoto Prefectural University of Medicine, Kyoto, Japan from 2002 to 2008.Preoperatively, PED existed on over more than 50% of the corneal surface in seven eyes. Severe ocular surface inflammation with fibrovascular tissue surrounded the PED in all 10 eyes. At 24-weeks postoperative, PED had improved in all cases except 1 in which the patient was unable to return to the hospital (95% CI, 55.5-99.7; Wilcoxon signed-rank test, p = 0.0078). The preoperative median of logarithmic minimum angle of resolution was 1.85 (range 0.15-2.70), and 1.85, 1.85, and 1.52 at the 4th, 12th, and 24th postoperative week, respectively. The mean total preoperative ocular surface grading score was 7.0 (range 4-17). At 4 and 12 weeks postoperative, the total ocular surface grading score had improved significantly (p = 0.0020, p = 0.0078), and at 24 weeks postoperative, it was 3.0 (range 2-12, p = 0.0234). During the follow-up period (median 23.3 months, range 5.6-39.7 months), no recurrence of PED was observed in any eye, and long-term ocular surface stability was obtained.COMET enabled complete epithelialization of PED and stabilization of the ocular surface in patients with severe ocular surface disease, thus preventing end-stage cicatrization and vision loss at a later stage.