WE REPORT HEREIN the case of an 18-year-old woman with trichotillomania who responded to low-dose fluvoxamine treatment. She consulted a dermatologist with complaints of continued hair-pulling at her scalp for 2 years. She was diagnosed as having trichotillomania because any skin disease was ruled out by the dermatologist. She was not depressed, and did not have any other anxiety disorders or tic disorders, and she had no family history of depression or obsessive–compulsive disorders, but her father was alcohol dependent, and he was sometimes verbally or physically violent with his wife and the patient when he drank alcohol. Severe hair loss was found in the temporoparietal and occipital areas on her head, but no scarring of her scalp was found. There was fine, short hair on the front of the head. She put on a cap to conceal her hair loss, and complained that she did not know why she did not stop pulling her hair. She was evaluated using the Massachusetts General Hospital Hair-pulling Scale (MGHHS), a clinical hair-pulling assessment battery consisting of seven questions and three components, for which the full score is 28 points.1,2 Her MGHHS and an actual-pulling subscale of the MGHHS (MGHHS-AP) were 21 and 9, respectively. In short, she was considered to have severe trichotillomania. Fluvoxamine was started at 25 mg/day, because this drug has little anticholinergic effects or weight gain. The plasma level of fluvoxamine was 9.5 ng/mL at a dose of 25 mg/day but MGHHS and MGHHS-AP scores were still 19 and 8, respectively after 2 weeks of treatment. The fluvoxamine dosage was increased to 50 mg/day, and her MGHHS and MGHHS-AP scores dropped to 14 and 6, respectively, at 2 weeks after the increase in fluvoxamine dosage. The plasma level of fluvoxamine was raised to 36.3 ng/mL at a dose of 50 mg/day. The fluvoxamine dosage was subsequently increased to 75 mg/day. Two weeks after this increase, her MGHHS and MGHHS-AP scores had decreased to 9 and 4, respectively. Her hair-pulling behavior dramatically improved, resulting in the re-growth of hair on her scalp. We monitored her plasma levels of fluvoxamine, and observed a plasma fluvoxamine level of 55.0 ng/mL at a dose of 75 mg/day. In short, she showed a remarkable improvement in the symptoms of trichotilliomania when treated with a low dose of fluvoxamine without any adverse effects. Trichotilliomania is considered to lie within the spectrum of obsessive–compulsive disorders, and serotonergic dysfunction might be involved in the pathophysiology of this condition. Stanley et al. reported that 300 mg/day of fluvoxamine was necessary to show efficacy in the treatment of 21 patients with trichotillomania.3 We previously reported a linear relationship between the dosage of fluvoxamine and plasma fluvoxamine concentrations, but there is a variation in plasma fluvoxamine levels between individuals based on patient metabolism when the dosage of fluvoxamine is administered.4 Therefore, measuring plasma levels of fluvoxamine might provide useful information on the patient's metabolism of fluvoxamine. The most important finding in the current study was that the patient responded to a low dose with a low plasma concentration of fluvoxamine. Therefore, slow titration of fluvoxamine might be ideal, because some trichotilliomanic patients might have resolution of symptoms on low-dose fluvoxamine.