To investigate the hypothesis that Huntington's Disease involves a breakdown in the organization of the lexico-semantic representational system, mildly and moderately demented patients with Huntington's Disease and age-matched normal control subjects were given a brief battery of language tests and a semantic priming free association task. Results of the language tests provided suggestive, but confounded, evidence for a semantic deficit in Huntington's Disease. Less equivocal evidence was yielded by results of the priming task, which showed a decline in the effect of association strength of primed stimulus-target word pairs on target hit rates. This finding was interpreted as a disruption in the system of spreading activation in a lexico-semantic network. This breakdown was contrasted with the more severe language deficits found in dementias which are primarily cortical in origin.