Advances in molecular biology have increased our understanding of both inherited and sporadic forms of neurological disease. In this review, the impact of these advances is discussed in relation to specific neurological conditions. These include the hereditary neuropathies and ataxias, Huntington's disease, and the muscular dystrophies, as well as Alzheimer's disease, Parkinson's disease, and motor neuron disease. Genetic channelopathies, such as familial hemiplegic migraine, are also described. Although knowledge in this area overall is still relatively scant, current advances in molecular biology have helped in the reclassification of some neurological disorders, thereby providing a further step towards the development of rational therapies to treat these conditions.