The proposed study is an 8-week, open-label trial of aripiprazole. The study would enroll 10 patients diagnosed with TTM meeting DSM-IV criteria. Subjects would start at a dose of 5 mg, which can be reduced to 2 mg if initial dose is not tolerated. Dose will be increased by 5 mg every two weeks (or as tolerated, with a minimum increase of 2 mg) until a maximum target dose of 15 mg is reached at the beginning of week 5. Dosing would not be increased if a patient showed clinical improvement at a lower dose (defined as a 30% reduction in Massachusetts General Hairpulling Scale) or was intolerant of a further dose increase. Dose may not be increased after week 5; at any point it may be decreased because of intolerability. Modified dosing of aripiprazole will not automatically happen if a patient is taking fluoxetine or paroxetine, but awareness that increased aripiprazole levels are associated with P450 2D inhibition (and consequent tolerability of a given dose) may factor into clinical decisions to increase, maintain or decrease aripiprazole dosage.