Thirty three eyes of 33 patients were prospectively evaluated to study the short term efficacy, and overall surgical outcome of initial trabeculectomy for primary glaucomas with adjunctive intraoperative on postoperative 5-Fluorouracil (5-FU) use. Twelve eyes served as control who underwent trabeculectomy without adjunctive antimetabolites. Eleven eyes received intraoperative 5-FU, while 10 eyes received subconjunctival 5-FU postoperatively. Intraocular pressure (IOP) was maintained below 22 mmHg at 3 months of follow up in 90.9% and 80% of patients in the intraoperative and postoperative 5-FU groups respectively, without use of additional antiglaucoma medications, whereas 66.7% of the patients in the control group achieved similar IOP levels. Hypotony (I.O.P. < 6 mmHg) was seen more commonly after intraoperative 5-FU (27.3%). Corneal epithelial defects were seen exclusively in the postoperative 5-FU group (40%). The use of intraoperative 5-FU exclusively as a mode of antimetabolite delivery seems an acceptable alternative to enhance success rates of trabeculectomy for the primary glaucomas.