Samples of cerebrospinal fluid (CSF) of 93 dogs with neurologic diseases were examined by cytomorphologic technique, and the changes in the CSF were correlated with histopathologic examinations of the central nervous system (CNS). It was concluded that CSF examination is a significant aid in obtaining a neurologic diagnosis and that good correlation exists between the CSF changes and the pathologic changes in the CNS. The CSF examination allows making a diagnosis of encephalitis and differentiation between viral and other causes (although in mycotic infection the cell membrane preparation can be used to identify the cause directly), could allow making differentiation between congenital malformations and congenital degenerative disease, and helps in identifying physical spinal cord damage, differentiating it from muscular, neurogenic, or functional disorders clinically presented as spinal ataxia. The CSF cytologic examination can indicate the presence of hemorrhage in the CNS. There is not enough experience available in the diagnosis of brain tumors by means of CSF examination; however, in dogs with lymphosarcoma in the CNS, CSF cytologic changes can be diagnostic.