InhaltsangabeMolecular Bases of Nucleotide Expansions.- Mechanisms of DNA Repeat Expansion.- Disorders Associated with Non-coding Repeats.- Molecular Correlates of Fragile X Syndrome and FXTAS.- The Neglected Fragile X Mutations: FRAXE and FRAXF.- Friedreich Ataxia.- Dodecamer Repeat Expansion in Progressive Myoclonus Epilepsy 1.- Myotonic Dystrophies Types 1 and 2.- Spinocerebellar Ataxia Type 8.- Recent Progress in Spinocerebellar Ataxia Type 10.- Disorders Associated with Coding Repeats.- Polyglutamine Diseases.- The Enigma of Spinocerebellar Ataxia Type 6.- Disorders Associated with Repeats in an Undetermined Location.- Spinocerebellar Ataxia Type 12 and Huntington's Disease-Like 2: Clues to Pathogenesis.- Postscript.- Current Issues and Therapeutic Prospects.