Eighteen patients with early Huntington's disease were compared with age- and IQ-matched control volunteers on tests of executive and mnemonic function taken from the Cambridge Neuropsychological Test Automated Battery. Tests of pattern and spatial recognition memory, spatial span, spatial working memory, spatial planning and visual discrimination learning/attentional set shifting were employed. These tests have previously been found to be sensitive to the later stages of Huntington's disease. Patients with early Huntington's disease were found to have a wide range of cognitive impairments encompassing both visuospatial memory and executive functions, a pattern distinct from those seen in other basal ganglia disorders. In contrast to patients with more advanced Huntington's disease, early Huntington's disease patients were not impaired at simple reversal learning, but were impaired at performing an extradimensional shift (EDS). The results will be discussed in relation to the hypothesized neuropathological staging of Huntington's disease and to the anatomical connectivity of the striatum.