The angle closure glaucomas are a diverse group of disorders characterized by mechanical blockage of the trabecular meshwork by the peripheral iris leading to elevated intraocular pressure and glaucoma. Understanding the pathophysiologic mechanisms underlying these disorders is essential for both diagnosis and management. This review covers the anatomy, etiology, classification, and therapy of the various angle closure glaucomas and the role that ultrasound biomicroscopy has played in helping us understand these diseases.