A late onset of cerebellar degeneration was diagnosed in a one-and-a-half-year-old Siamese cat. The animal had been presented with mild ataxia involving all four limbs. Over the following two years, the signs gradually progressed to severe incoordination, a frequent tendency to fall and a head tremor. The neurological signs were consistent with a diffuse cerebellar lesion and the cat was euthanased. Profound and diffuse Purkinje cell loss was found on histopathological examination, but no aetiological agent was detected.