We treated a 40-year-old man with an acute, unilateral, open-angle glaucoma caused by a gelatinous translucent material in the anterior chamber. A clinical diagnosis of mucogenic secondary open-angle glaucoma caused by diffuse epithelial ingrowth after ocular trauma one year earlier was suspected, but a primary or secondary ciliary body or iris neoplasm could not be ruled out. A curative 9-mm block-excision was performed. Six years later, intraocular pressure was normal, and the visual function was unchanged. Light and electron microscopy disclosed an island of diffuse columnar epithelium with numerous goblet cells on the iris surface and copious mucinous material extending into the trabecular mesh-work.