Inclusion Criteria:

1. Age 18+
2. Written informed consent.
3. Meet DSM-IV criteria (by SCID) for alcohol dependence.
4. Meet DSM-IV criteria (by SCID) for bipolar disorder I or II disorder.
5. ≥ 8 heavy drinking days (defined as ≥ 5 standard drinks per day for men, ≥ 4 standard drinks per day for women) in the prior 4 weeks.
6. During the baseline visit, patients must be on a stable dose of accepted maintenance treatment for bipolar disorder for the past 4 weeks. If the subject is on more than one agent, at least one agent must be adequately dosed.
7. Antidepressant treatment is permitted if the dose has been stable for the past 4 weeks.

Exclusion Criteria:

1. Pregnant women or women of child bearing potential who are not using a medically accepted means of contraception (condom, diaphragm, spermicide, intrauterine device, tubal ligation, or partner with vasectomy). Because of the risk of the lowering of oral contraceptive blood levels with topiramate, women whose sole means of contraception is oral contraceptives or hormonal implants will be asked to use an additional barrier method of birth control during treatment with the study drug.
2. Women who are lactating.
3. Age under 18.
4. Patients who do not have ≥ 8 heavy drinking days in the 4 weeks prior to the baseline visit.
5. Important alcohol withdrawal symptoms (Clinical Institute Withdrawal Assessment for Alcohol-Revised, CIWA-Ar, score > 15)
6. Urine toxicological screen positive for amphetamines or cocaine.
7. Meets DSM-IV criteria for current substance dependence for drugs other than cannabis or nicotine.
8. Currently meets full DSM-IV criteria for manic, hypomanic, or mixed episode.
9. Serious suicide or homicide risk, as assessed by evaluating clinician.
10. Unstable medical illness including cardiovascular, hepatic, renal, respiratory, endocrine, neurological, or hematological disease or uncontrolled seizure disorder.
11. History of nephrolithiasis, or treatment with any drug associated with nephrolithiasis.
12. Current treatment with zonisamide.
13. Current treatment with any carbonic anhydrase inhibitors, including acetazolamide, dorzolamide, and methazolamide.
14. Current treatment with any drug known to decrease drinking.
15. Subjects who have begun a new psychosocial treatment within 12 weeks of study enrollment. Subjects receiving psychosocial treatment that has been stable for at least 12 weeks prior to study entry, however, will be permitted to enroll in the study.
16. Any psychotic disorder, including schizoaffective disorder (current or past).
17. Clinical or laboratory evidence of untreated hypothyroidism.
18. Patients with a diagnosis or history of glaucoma
19. Patients requiring excluded medications (see table below for details).
20. Psychotic features in the current episode or a history of a psychotic disorder, as assessed by SCID.
21. Past intolerance to topiramate.
22. Any use of topiramate in the past 12 months.
23. Any investigational psychotropic drug within the last 3 months.