Ab externo thermal sclerostomy was performed with the holmium YAG (thulium, holmium, chromium-doped YAG crystal) laser in 21 eyes of 20 patients with refractory glaucoma. We used either the 5-fluorouracil (5-FU) or mitomycin C (MMC) antimetabolites in all cases. The rate of intraocular pressure (IOP) control defined as IOP < 21="" mmhg="" regardless="" of="" whether="" antiglaucoma="" medication="" was="" applied="" postoperatively)="" was="" estimated="" by="" the="" life-table="" methods="" of="" kaplan-meier.="" the="" postoperative="" iop="" control="" rate="" was="" 47.1%="" in="" the="" mmc-treated="" group="" at="" 57="" months,="" and="" 14.3%="" in="" the="" 5-fu-treated="" group="" at="" 52="" months.="" there="" were="" statistically="" significant="" differences="" in="" success="" rates="" between="" the="" mmc-="" and="" 5-fu-treated="" groups.="" we="" observed="" no="" clinically="" significant="" complications="" except="" excess="" filtration="" associated="" with="" a="" shallow="" anterior="" chamber="" in="" one="" case.="" this="" procedure="" is="" thought="" to="" have="" several="" advantages="" over="" more="" conventional="" filtration="" surgery;="" the="" operation="" time="" is="" shorter,="" and="" there="" is="" no="" need="" for="" intraocular="" manipulation,="" which="" means="" conjunctival="" trauma="" is="" minimal.="" however,="" the="" iop="" control="" rate="" was="" substantially="" lower="" than="" that="" achieved="" via="" conventional="" trabeculectomy.="" our="" results="" suggest="" that="" the="" selection="" of="" patients="" and="" the="" use="" of="" mmc="" is="" an="" important="" factor="" in="" maintaining="" successful="">