Ocular disease is one of the most common problems encountered in sea lions at various zoos and aquariums around the world.1 The California sea lion (Zalophus californianus) is one of the most common marine mammals maintained in zoos and is also the most commonly afflicted with ocular disease. Studies have shown that pinnipeds housed in captivity manifest an array of ocular lesions.2 Eye disease can range from a pinpoint corneal opacity to loss of vision due to keratopathy, cataracts and secondary glaucoma. Glaucoma is a disease that has not been extensively studied in the sea lion.3 Observation of clinical signs and determination of intraocular pressures (IOP) are critical for early diagnosis. IOP measurement may elucidate intraocular disease and provides information on the balance between aqueous humor production and outflow. The objective of this study is to measure IOP in California sea lions that have clinically normal eyes as well as those with varying degrees of ocular diseases, and to evaluate the incidence of secondary glaucoma in this species.