The CAG Triplet Repeat Disorders are a group of largely untreatable inherited neurological disorders which result from an expansion in a CAG trinucleotide repeat in the mutant genes. This group of diseases includes Huntington’s disease, spinal and bulbar muscular atrophy, and several of the spinocerebellar ataxias. In each case, the CAG repeat lies within the coding region of a gene and results in an abnormally long polyglutamine tract within the mutant protein. Marked similarities in the underlying genetics and neuropathology suggest common pathologic mechanisms among these disorders. The 2009 Gordon Conference on CAG Triplet Repeat Disorders and the associated Gordon Research Seminar (GRS) will gather together young investigators and established senior scientists to deliver provoking lectures on the cutting-edge of science. Topics will include a clinical and pathological overview, circuitry malfunction, synaptic pathology, novel neuroimaging techniques, repeat instability, RNA gain of function, bidirectional expression, new animal models, and genetic modifiers. Strong emphasis is placed on training and mentoring of young scientists, and time will be devoted to career issues. All participants will be required to present posters. Some poster presenters will be selected for short talks. The collegial atmosphere of this Conference, with programmed discussion sessions as well as opportunities for informal gatherings in the afternoons and evenings, provides an avenue for scientists from different disciplines to brainstorm and promotes cross-disciplinary collaborations in the various research areas represented. Priority will be given to women, minorities and persons with disabilities when selecting participants.