Inclusion Criteria:

1. Mania or mixed episode of bipolar disorder according to DSM-IV
2. Male and female between the age of 18 and 65 (In case of child-bearing women, negative pregnancy test results should be confirmed before the administration of the investigational drug and appropriate contraception be used. Pregnant and breast-feeding women cannot be included)
3. Patients who can consent to participate in this clinical trial
4. Patients who understand this trial and comply with all protocol requirements
5. Patients who fulfill the following remission criteria for bipolar disorder in the two consecutive evaluation performed every week at Week 6 of 6-week study and thereafter: (Definition of remission: a score less than 12 on the YMRS total score and simultaneously a score less than 13 on the MADRS total score)

Exclusion Criteria:

1. Patients with the following clinical symptoms diagnosed using DSM-1. Patients with the following clinical symptoms diagnosed using DSM-IV:

   • Delirium, dementia, amnestic or other cognitive disorders
   • Schizophrenia or schizoaffective disorder
2. Patients who do not respond to clozapine
3. Patients who are expected to require the administration of prohibited concomitant drugs during the clinical trial period
4. Patients diagnosed with substance-related disorder according to DSM-IV within the past 3 months (abuse, intoxication, dependency and/or withdrawal symptoms). The abuse of benzodiazepines is included with the exception of caffeine or nicotine.
5. Patients known to have allergy or hypersensitivity reaction to Abilify(aripiprazole) or other quinolinones
6. Patients at high risk of suicide attempt or with the history of murder or mental status test
7. Patients with the history of neuroleptic malignant syndrome
8. Patients with the past history which may cause serious adverse events that can affect the safety or efficacy evaluation during the clinical trial period
9. Patients with clinically significantly abnormal laboratory results, vital sign or ECG results
10. Pregnant women or child-bearing women who do not or cannot use appropriate contraception
11. Patients with the history of convulsive disorder
12. Patients judged to have decreased compliance to the investigational drugs during a 6-week trial period by an investigator
13. Patients who commit serious protocol violation during a 6-week trial