The primary objective of this study is to assess the efficacy of varenicline in reducing the proportion of heavy drinking days during the last 8 weeks of treatment in subjects with alcohol dependence confirmed by Diagnostic and Statistical Manual of Mental Disorders-IV-Text Revision (DSM-IV-TR) criteria and who frequently consume 10 or more drinks per drinking day for men and 8 or more drinks for women (designated as "very heavy" drinkers).

Inclusion Criteria:

1. Be at least 18 years of age.

2. Have a current (past 12 months) DSM-IV-TR diagnosis of alcohol dependence.

3. Be seeking treatment for alcohol dependence and desire a reduction or cessation of drinking.

4. Be able to verbalize an understanding of the consent form, able to provide written informed consent, verbalize willingness to complete study procedures, able to understand written and oral instructions in English and able to complete the questionnaires required by the protocol.

5. Agree (if the subject is female and of child bearing potential) to use at least one of the following methods of birth control, unless she is surgically sterile, partner is surgically sterile or she is postmenopausal:

   1. oral contraceptives,
   2. contraceptive sponge,
   3. patch,
   4. double barrier (diaphragm/spermicidal or condom/spermicidal),
   5. intrauterine contraceptive system,
   6. levonorgestrel implant,
   7. medroxyprogesterone acetate contraceptive injection,
   8. complete abstinence from sexual intercourse,
   9. hormonal vaginal contraceptive ring, and/or

6. Be able to take oral medication and be willing to adhere to the medication regimen

7. Complete all assessments required at screening and baseline.

8. Provide evidence of stable residence in the last 2 months prior to randomization, have reasonable transportation arrangements to the study site, and have no plans to move within the next 3 months or unresolved legal problems. Subjects must provide contact information of someone, such as a family member, spouse, or significant other, who may be able to contact the subject in case of a missed clinic appointment.

9. Be willing to discontinue the use of nicotine replacement therapies prior to randomization and refrain from using nicotine replacement therapies during the course of the study.

10. Have a blood alcohol content (BAC) by breathalyzer equal to 0.000 when s/he signed the informed consent document.

11. Be someone who in the opinion of the investigator would be expected to complete the study protocol.

12. Agree to the schedule of visits, verbally acknowledge that s/he will be able to attend each scheduled visit, participate in phone visits and that s/he does not have any already scheduled events or a job that may interfere with study participation.

One subject (two records) was excluded from analysis due to his dual study participation at two separate clinical sites. Both instances of participation were in the Varenicline arm and both instances were not considered in the mITT population.

AEs were assessed by virtue of an open ended question and by subject report.