The few reports available on olanzapine in Huntington's disease (HD) are insufficiently documented and/or insufficiently dosed. We describe a 30-year-old woman with genetically confirmed HD who presented with severe chorea. She was not able to eat or dress without help and did not respond to haloperidol; the motor scale of the Unified HD Rating Scale (UHDRS-I) revealed 65 of a possible 124 points. After admission, we treated the patient with a high dose of olanzapine (30 mg daily). The chorea almost ceased in the next 2 days, she was able to eat and walk without assistance (UHDRS-I of 21 points), and fine motor tasks improved, as well as gait and eye movements. This effect lasted for 5 months. We conclude that high-dose olanzapine appears to be useful in grave choreatic attacks.