We evaluated perioperative conjunctival biopsy specimens in 28 consecutive patients with primary open-angle glaucoma undergoing trabeculectomy who had not undergone previous intraocular surgery. We found six months postoperatively that the number of goblet cells was significantly greater (6.40 +/- 5.40 vs 1.68 +/- 1.60 per field of view; P = .004, Student's t-test) in patients with easier postoperative intraocular pressure control (intraocular pressure < or = 15 mm Hg with zero to two glaucoma medications) than in patients with more difficult intraocular pressure control (> 15 mm Hg with three or more glaucoma medications). No statistical differences between groups were observed in mast cells, neutrophils, eosinophils, macrophages, plasma cells, lymphocytes, or fibroblasts (P > .05). Also, no statistical difference between groups existed in conjunctival structure, including mucopolysaccharide and collagen composition, vascular density, or epithelial thickness (P > .05). This study suggests that the number of conjunctival goblet cells may be related to intraocular pressure control after trabeculectomy.