Previous reports on the use of olanzapine in Huntington's disease (HD) used doses ranging from 10-30 mg. We report a case of HD with marked delusions and behavioral impairment assessed by the Unified Huntington's Disease Rating Scale at baseline and four months later treated with a low dose of olanzapine. The patient improved in motor, psychiatric and activity of daily living symptoms after four months of treatment. The response to a low dose of olanzapine in HD may be an indicator of efficacy in similar cases. Further randomized controlled trials can properly assess these findings.