Abstract: In order to investigate age-related morphological changes in the white matter of the lumbar spinal cord in young adult and old cats, several techniques were used. (1) Immunostaining of neurofilaments (NF) was used to identify nerve fibres; (2) modified Holzer crystal violet to show all the glial cells; (3) immunoreaction of glial fibrillary acid protein (GFAP) to exhibit the astrocytes; (4) the Golgi method to display the morphology of glial cells and astrocytes in the white matter. Under the microscope, the fibres and glial cells were observed and quantitatively studied. Compared with young cats, old cats showed significantly lower density of nerve fibres (P<0.01)and weaker staining of the NF immunoreactivity. However, the density of glial cells and astrocytes (P<0.01) in old cats is significantly greater than in young adult cats. In addition, astrocytes in old cats were more hypertrophic, with stronger immunoreactivity of GFAP substance than in young ones. This indicates that there is a loss of nerve fibres accompanied by an obvious glial hyperplasia in the white matter of the aging cat spinal cord. The above results suggest that the loss of nerve fibres in the white matter of old cats may be an important factor that underlies the functional decline of signal transmission and processing in the spinal cord during ageing. The activity enhancement of glial cells in old cats may provide a protective effect on surviving nerve fibers from further degradation during senescence.