Huntington's disease (HD) is a hereditary neurodegenerative disorder that gradually robs sufferers of the ability to control movements and induces psychological and cognitive impairments. This devastating, lethal disease is one of several neurological disorders caused by trinucleotide expansions in affected genes, including spinocerebellar ataxias, dentatorubral-pallidoluysian atrophy, and spinal bulbar muscular atrophy. HD symptoms are associated with region-specific neuronal loss within the central nervous system, but to date the mechanism of this selective cell death remains unknown. Strong evidence from studies in humans and animal models suggests the involvement of energy metabolism defects, which may contribute to excitotoxic processes, oxidative dmage, and altered gene regulation. The development of transgenic mouse models expressing the human HD mutation has provided novel opportunities to explore events underlying selective neuronal death in HD, which has hitherto been impossible in humans. Here we discuss how animal models are redefining the role of energy metabolism in HD etiology.