Experimental: After obtaining informed consent, 100 patients with bipolar I, or II disorders and alcohol abuse/dependence confirmed by a structured clinical interview (SCID) will be enrolled. from referral sources in the community we have developed over the past 3 years. A medical history and physical examination, including an eye exam with an ophthalmoscope, will also be performed at baseline to rule out serious medical illnesses and cataracts. Baseline labs including a liver panel and CBC will be obtained. Women of child-bearing potential will be given a urine pregnancy test. Baseline measures of psychiatric symptoms will be assessed with the HRSD, YMRS, and Barratt Impulsiveness Scale. Alcohol cravings will be assessed with the Obsessive Compulsive Drinking Scale (OCDS). Alcohol use including number of drinks/2 weeks, days used in the past two weeks, and days of heavy use will be obtained as will a urine drug/alcohol screen. Alcohol use and cravings will also be recorded throughout the study. Side-effects will be assessed with a general side effects scale, the Abnormal Involuntary Movement Scale (AIMS), Simpson-Angus Scale (SAS), and Barnes Akathesia Rating Scale (BARS). GGT levels will also be repeated at weeks 6 and 12. The subjects will be randomized and receive quetiapine or identical appearing placebo add-on therapy in a double-blind fashion for 12 weeks. Subjects will return every two weeks for reevaluation with the above outcome measures and for upward titration of study drug. All subjects will be given the option of receiving open-label quetiapine for an additional 4 weeks (with continuing assessment of mood and alcohol use/cravings every 2 weeks) at the end of the study or discontinuing medication.