In this study it was aimed to compare the pathological findings on the brains of aged and young dogs. The research material consisted the brains of 20 dogs over 10 years old and brains of 10 dogs with an age of 1-2 years old. The brains were first of all examined macroscopically afterwards the tissue samples were taken from telencephalon, mesencephalon, rhombencephalon for histopathological and immunohistochemical investigations. In the aged dogs brains macroscopic examinations revealed meningeal thickness and ventricular dilatation. Microscopically, fibrosis at choroid plexus, meninges and vascular walls also ependymal defects, gliosis and neuronal depletion were observed in the aged dogs brains. On semi quantitative examination of the sections, a statistically significant increase on Glial Fibrillary Acidic Protein (GFAP) and 2',3'-Cyclic Nucleotide 3'-Phosphodiesterase (CNPase) expressions were determined in old dogs compared to young dogs (P<0.01).