The purpose of this study was to investigate the effect of age on endothelial morphology and morphometry in cats. The corneal endothelium was studied through contact specular microscopy. A total of 18 cats were evaluated in this study. The cats were euthanatized for reasons unrelated to this study and died of disease that did not directly affect the eye. All studies were approved by the institutional Animal Care and Use Committee and were performed in compliance with the Association for Research in Vision and Ophthalmology statement on the use of animals in ophthalmic and vision research. Ophthalmic examination was performed before enucleation. The subjects were divided in three groups with six cats (Felis catusLINNAEUS, 1758) in function of age: G1 (1 to 3 months old), G2 (5 to 12 months old), and G3 (24 to 40 months old). Eyes were mounted on an eyeball holder and examined using a contact specular microscope (BioOptics®, model LSM2100 C, Inc. Arlington, MA, EUA) with software for corneal endothelium analysis. Specular microscopy was performed on all eyes in orders to determine the conditions of the corneal endothelium and those with evidence of alteration were excluded. All analyses were carried out by the same investigator. Three micrographs of the corneal endothelium were taken from the central region of each cornea. The corneal endothelial cell analysis was done with a variable frame analysis method. A minimum of 100 well defined endothelial cells obtained from each frame was analyzed. The endothelial cell density, mean cell area, polymegathism and pleomorphism were obtained from both eyes. Statistical analysis was performed using variance analysis and Tukey test with significance at p < 0.05. The results reveled decrease of cell density with age, the average cell area and pleomorphism increase as function of age. The polymegathism showed constant values on the three groups. The present work demonstrates that the cat corneal endothelium has mitotic limited activity. Moreover, with advancing age the mean cell area increase and cell density decrease.