Patients with Huntington's disease (HD) were compared to normal controls of equivalent age and verbal intelligence on a set of verbal learning tasks. Although the HD patients showed the expected deficit in secondary (long-term) memory, their performance was otherwise comparable to that of the control groups. Primary (short-term) memory was normal, there was normal sensitivity to proactive interference, and the patients showed an advantage, albeit reduced, in recall of related compared to unrelated word lists. The findings suggest that mnemonic input is encoded semantically in HD though less efficiently than in unafflicted individuals, and that difficulty accessing information in semantic (knowledge-based) memory may be partially responsible for the memory disorder of HD.