Immunochemical staining to detect ubiquitin has become an essential technique in evaluating neurodegenerative processes. Age related staining is seen in myelin, in nerve processes in lysosome‐related dense bodies, and in corpora amylacea. There is a constant association between filamentous inclusions and the presence of ubiquitin. Intermediate filaments associated with ubiquitin, α B crystallin and enzymes of the ubiquitin pathway are the basis of Lewy bodies and Rosenthal fibres, as well as related bodies outside the nervous system. Neurofibrillary tangles in diverse diseases are associated with ubiquitin as are several othertaucontaining inclusions in both neurones and glia. Inclusions in motor neurones and non‐motor cortex characterizing amyotrophic lateral sclerosis (ALS) and certain related forms of frontal lobe dementia can only be readily detected by anti‐ubiquitin. Anti‐ubiquitin also identifies both filamentous and lysosomal structures in neuronal processes as well as in some swollen neurones. Involvement of ubiquitin‐containing elements of the lysosomal system appears important in pathogenesis of prion encephalopathies. Despite great advances in understanding cell biology of the ubiquitin pathway there are as yet few insights into the precise role played by ubiquitin in neuron