Trabeculectomy specimens from three eyes with Sturge-Weber syndrome were examined histopathologically. Changes in the trabecular meshwork-Schlemm's canal system were similar to findings in old age and in primary open-angle glaucoma. Two mechanisms for glaucoma are theorized. In cases with buphthalmos and congenital glaucoma, the chamber angle is often anomalous, as in other types of congenital glaucoma. In later onset juvenile cases, the chamber angle more often appears normal. A premature aging of the trabecular meshwork Schlemm's canal complex, as shown by us histopathologically, is a primary cause of juvenile glaucoma. It is suggested that both mechanisms relate to the abnormal hemodynamics of episclera and chamber angle, due to persistence of Streeter's primordial vascular plexus.