The current status of research into chromosomal abnormalities in neurological diseases is reviewed. The only possible association between chromosome aberration and neurological disorder is found in ataxia telangiectasia and in tumours of the nervous system. In the remaining diseases reviewed, no specific association was confirmed. This was expected to some extent, since the majority of these diseases (spinal muscular atrophies, muscular dystrophies, etc.) are due to single gene defects.