BACKGROUND: In general, effective treatments for trichotillomania have been elusive. Although behavioral therapies and hypnosis have provided benefits to some, adult patients with chronic hair pulling have often proved refractory to treatment. Medication has generally been unhelpful until the recent introduction of serotonin reuptake inhibitors for the treatment of this condition. Furthermore, there has been little systematic study of the clinical characteristics of these patients. METHOD: Twenty individuals with trichotillomania were interviewed and were characterized on the basis of hair-pulling patterns, comorbidity, obsessionality, and the presence of symptoms of depression and anxiety. Twelve patients participated in an open 16-week trial of fluoxetine (up to 80 mg/day). RESULTS: Compared with baseline scores derived from a scale of trichotillomania severity, severity scores at endpoint decreased (improved) by 34% (p less than .025). Among the 8 responders, the mean decrease in severity scores was 60%. Fifty-five percent (11 of 20) had current or past additional DSM-III-R Axis I diagnoses (disorders of mood, anxiety, and psychoactive substance use). CONCLUSION: We conclude that in an open 16-week trial, patients treated with fluoxetine improved significantly. Data are presented on comorbid conditions, depressive symptoms, and anxiety. Baseline behavioral assessments of patients with trichotillomania suggest that substantial differences exist between this syndrome and obsessive compulsive disorder.