Huntington's disease (HD) is a devastating autosomal-dominant neurodegenerative condition caused by a CAG repeat expansion in the gene encoding huntingtin which is characterised by progressive motor impairment, cognitive decline and neuropsychiatric disturbances. There are currently no disease-modifying treatments available to patients, but a number of therapeutic strategies are currently being investigated, chief among them are nucleotide-based 'gene silencing' approaches, modulation of huntingtin post-translation modification and enhancing clearance of the mutant protein. In 2008, the authors' review highlighted the need to develop and validate biomarkers and provided a systematic head-to-head comparison of such measures. They searched the PubMed database for publications, which covered each of the subheadings mentioned below. They identified from these list studies which had relevance to biomarker development, as defined in their previous review. Building on a tradition of collaborative research in HD, great advances have been made in the field since that time and a range of outcome measures are now being recommended in order to assess efficacy in future therapeutic trials.