PURPOSE. To investigate whether topical administration of pirfenidone eye drops could be used to prevent postoperative scarring in a rabbit model of experimental glaucoma filtration surgery. METHODS. In a randomized, controlled, masked-observer study, 40 rabbits underwent trabeculectomy in the right eyes and randomly received postoperative administration of 0.1% or 0.5% pirfenidone, perioperative mitomycin C (0.25 mg/mL), or no treatment. Bleb characteristics and functions were evaluated over a period of 4 weeks. The animals were killed on days 7, 14, and 28. Histopathology and immunohistochemistry were performed to determine the amount of scarring and fibrosis. Ocular toxicity was assessed by the Draize test, histopathology, and electron microscope. RESULTS. The four treatment groups were similar with respect to intraocular pressure and anterior chamber depth. Pirfenidone 0.5% significantly prolonged bleb survival, and the blebs were larger and higher than those in the control group (P < 0.05); the 0.1% pirfenidone concentration was less effective. Furthermore, the histology and immunohistology results showed that the 0.5% pirfenidone and mitomycin C groups had less scarring at days 7 to 28 than did the controls. Toxicity assessments showed that pirfenidone did not damage the rabbit eyes. CONCLUSIONS. Postoperative use of 0.5% pirfenidone eye drops was associated with improved trabeculectomy bleb survival in a rabbit model. Pirfenidone eye drops may be a safe and effective antiscarring agent in glaucoma filtration surgery. (Invest Ophthalmol Vis Sci. 2011;52:3136-3142) DOI:10.1167/iovs.106240