Failure of a glaucoma filtering surgery mainly results from scarring at thefiltering wound. Postoperative proliferation of fibroblasts plays an imrortant role in scar tissue formation. Colchicine is a cytoplasmic microtubule inhibitor capable of inhibiting fibroblast proliferation. The effect of colchicine on fibroblast proliferation at the filtering wound after filtering surgery was investigated. Posterior lip sclerectomies were performed in each eye of albino rabbits.Intraocular pressures, conjunctival fibrosis, histologic findings and drug tox-icities were examined postoperatively under the topical or oral administration of colchicine. Reductions of intraocular Pressure and conjunctival fibrosis in colchicinetreated groups after filtering surgory were statistically significant (p< 0.05), and changes in the topical administration group were more significant than in the oral administration group (pl 0.05). Histologicallyr reductions of active fibroblasts and collagen fibers at the filtering wound and the subconjunctival area were seen in colchicine treated eyes.Histologic changes were more prominent in the topical administration group. Signs of orular and systemic toxicity were absent. The above results suggest that administration of colchicine, especially topicaladministration, can increase the success rate of filtering surgery.