The purpose of this study is to evaluate the safety, efficacy, and tolerability of twice daily (BID) administration of three dose strengths (1.2 mg, 1.8 mg, and 2.4 mg) of varenicline controlled release (CR) tablets in adult smokers.

Inclusion Criteria:

• Male or female cigarette smokers between the ages of 18 and 75 years, inclusive, who are motivated to stop smoking.
• Females of non-childbearing potential (surgically sterilized or at least 2 years postmenopausal) who are not nursing may be included.
• Subjects must have smoked an average of at least 10 cigarettes per day during the past year and over the month prior to the screening visit, with no period of abstinence greater than 3 months in the past year.

Exclusion Criteria:

• Subjects with clinically significant cardiovascular disease in the past 6 months.
• Subjects hospitalized within the past 12 months due to suicidal ideation or suicidal behavior or subjects considered to have serious suicidal ideation or suicidal behavior within the past 12 months.
• Subjects having active suicidal ideation or behavior identified at Screen or Baseline.
• Subjects currently or within the past 12 months requiring treatment for depression. Subjects with current or prior history of panic disorder, anxiety disorder, hostility or aggression disorder, perceptual/thinking disturbances, psychosis, or bipolar disorder.