Congenital syphilis is caused by Treponema pallidum infection through the placenta in the embryonic stage and causes ophthalmic symptoms in childhood and adulthood. Ocular involvement of congenital syphilis consists of interstitial keratitis, anterior uveitis, acute iridocyclitis, chorioretinitis, perivasculitis, optic neuritis and secondary glaucoma. Interstitial keratitis and anterior uveitis usually occur between the ages of 5 and 20 years [1] but secondary glaucoma due to congenital syphilis occurs an extremely long time, 30 or 40 years, after interstitial keratitis [2][3][4]. Knox suggests that low-grade, subclinical recurrence of keratitis involves the trabeculae in the inflammatory process and produces a rapid rise in resistance to aqueous outflow [2]. Sugar supposes that trabecular space obstruction and pathologic alterations cause late glaucoma associated with interstitial keratitis [5] but the mode of obstruction in the angle has not yet been reported. We conducted a histopathological study of secondary glaucoma due to congenital syphilis to clarify the reason for increased intraocular pressure (IOP) using trabeculectomy (TLE) specimens.