A 9-month-old domestic shorthair cat was humanely killed because of uncoordinated gait, myoclonus, seizures and reduced vision. Histological, immunohistochemical and ultrastructural examination revealed a neuronal storage disease consistent with neuronal ceroid-lipofuscinosis (NCL). Neurons contained Sudan black- and luxol fast blue-positive material which was autofluorescent. Immunohistochemically, the storage material was found to contain subunit c of mitochondrial ATP synthase, a protein recently recognized as the main component of the storage material in NCL. Ultrastructurally, the material consisted of curvilinear and fingerprint bodies, which are indicative of NCL.