To investigate the effects of postoperative mitomycin C (MMC) eyedrop as an adjunct to intraoperative MMC in refractory glaucomas, 15 eyes of 14 glaucoma patients (age; 47.0 ± 15.5 years) in need of trabeculectomy were studied. Preoperative diagnoses were secondary glaucoma to uveitis in seven patients, neovascular glaucoma in four, pseudophakic glaucoma in three, and aphakic glaucoma in one. Six patients who had neovascular glaucoma or history of a failed trabeculectomy with intraoperative 0.2 mg/ml MMC received intraoperative 0.4 mg/ml MMC. The others received 0.2 mg/ml MMC for 3 minutes. During the follow-up period, postoperative MMC eyedrop was applied, depending on the condition of the filtration bleb. The eyedrop was 0.2 or 0.4 mg/ml, applied four times a day for one week. The follow-up period was 18.1 ± 7.4 months. The success rates were 93.3%, 86.7%, and 78.0% at postoperative 1, 4, and 18 months, respectively. There was neither early hypotony nor wound leak. Corneal epithelial defects (26.7%), corneal ulcers (6.7%), and cataracts (6.7%) were, however, observed. Postoperative MMC eyedrop application was a convenient and effective adjunct to intraoperative MMC in refractory glaucomas.