Glaucoma is a disease complex in which one of several exciting factors is responsible for an elevation of the intraocular pressure beyond its normal physiological limitations. At present two types of primary glaucoma may be described for the dog, while the recognition of secondary glaucoma as a complication to lens luxation, uveitis, trauma, infection and neoplasia has long been established. Identification of the causal factor within this complex plays a necessary part in the institution of successful treatment.