Background: Thus far, only selective serotonin reuptake inhibitors have been systematically studied in the treatment of trichotillomania, and the results are conflicting. This open-label study is the first to systematically evaluate an atypical neuroleptic, olanzapine, as a monotherapy in the treatment of trichotillomania. Method: Twenty-one patients were screened and 18 patients were enrolled in a 3-month open-label study of olanzapine for trichotillomania (diagnosis based on modified DSM-IV criteria). Patients with comorbid psychiatric disorders or on treatment with psychoactive medication were excluded. Olanzapine was titrated gradually in 2.5-mg/week increments up to a maximum dose of 10 mg/day. Results: Seventeen patients who completed at least 1 week of olanzapine treatment were evaluated. Hair pulling, as measured by the Massachusetts General Hospital Hairpulling Scale, decreased by 66% from baseline (p ≤.001), and mean scores on the Hamilton Rating Scale for Anxiety decreased by 63% (p ≤ .05). Clinical Global Impressions scale scores also revealed significant improvement as a whole (p ≤ .001), with 4 patients having complete symptom remission at the end of the study period. Conclusion: Findings suggest that olanzapine may be an effective monotherapy for trichotillomania.