Inclusion Criteria:

- Between 18 and 65 years of age who self-report smoking at least 5 cigarettes (menthol
and non-menthol) per day, on average.

- Diagnosed with HIV infection and exhibiting viral load of < 75 copies/mL and CD4+
counts of > 200 cells/mm3 within 6 months prior to enrollment.

- Able to use varenicline safely, based on a medical evaluation including medical
history and physical examination, and psychiatric evaluation.

- Residing in the geographic area for at least 7 months.

- Women of childbearing potential (based on medical history and physical exam) must
consent to use a medically accepted method of birth control (e.g., condoms and
spermicide, oral contraceptive, Depo-Provera injection, contraceptive patch, tubal
ligation) or abstain from sexual intercourse during the time they are taking study
medication and for at least one month after the medication period ends.

- Able to communicate fluently in English.

- Capable of giving written informed consent, which includes compliance with the
requirements and restrictions listed in the combined consent/HIPAA form.

Exclusion Criteria:

Smoking Behavior

- Current enrollment or plans to enroll in another smoking cessation program in the
next 7 months.

- Regular (daily) use of chewing tobacco, snuff, snus, cigars, cigarillos, or pipes.

- Current use or plans to use nicotine substitutes (gum, patch, lozenge, e-cigarette)
or smoking cessation treatments in the next 7 months.

1. Note: Once participants are found eligible for the study, they are told they
should refrain from using any nicotine replacement therapy (NRT) for the
duration of the study. If a subject reports an isolated (non-daily) instance of
NRT use during the study, they may be permitted to continue.

Alcohol/Drug Exclusion Criteria

- Current untreated and unstable diagnosis of substance abuse or dependence (eligible
if past use and if receiving treatment and stable for greater than or equal to 30
days).

- Positive urine drug screen (for cocaine and/or methamphetamines) at the Intake
Session.

- Breath Alcohol Concentration (BrAC) assessment greater than or equal to 0.01 at the
Intake Session.

Medication Exclusion Criteria

Current use or recent discontinuation (within last 14 days) of the following medications:

- Other smoking cessation medications (e.g. Zyban, Wellbutrin, Wellbutrin SR, Chantix)

a. Note: Once participants are found eligible for the study, they are instructed to
only use the smoking cessation medication provided to them by the study staff. If a
subject reports an isolated (non-daily) instance of using a non-study smoking
cessation medication, the study physician and PI will evaluate the situation and
determine if it is safe for the subject to continue participation.

- Anti-psychotic medications.

- Bipolar Disorder medications.

Medical Exclusion Criteria

- Women who are pregnant, planning a pregnancy within the next 7 months, or lactating.

- Current diagnosis of unstable and untreated major depression, as determined by
self-report & MINI (eligible if stable for greater than or equal to 30 days).

- Current or past diagnosis of psychotic or bipolar disorder, as determined by
self-report or MINI.

- Any suicide risk score on MINI, current suicidal ideation on Columbia scale, or
self-reported lifetime suicide attempt.

- History of cancer diagnosis (excluding non-metastasized (Stage 1) skin cancer).

- History of heart disease, stroke or MI, unstable angina, or tachycardia (if stable,
requires Study Physician approval).

- Uncontrolled hypertension (SBP >160 or DBP >100).

a. Note: If a participant presents with blood pressure greater than 160/100 at
sessions occurring on Week 0 (Pre-Quit) or at any other point during the treatment
period, they will not be provided with/able to continue on medication unless the
study physician grants approval.

- History of kidney or liver failure.

- Abnormal ECG (unless approved by study physician).

- Estimated creatinine clearance <50 mL/min, within 6 months prior to enrollment.

- AST and/or ALT results greater than 2 times the upper limit of normal, within 6
months prior to enrollment.

- Any impairment (physical, neurological, visual) preventing cognitive task
performance.

- Previous allergic reaction to varenicline.

General Exclusion Criteria

- Any medical condition or concomitant medication that could compromise subject safety
or treatment, as determined by the Principal Investigator and/or Study Physician.

- Inability to provide informed consent or complete any of the study tasks as
determined by the Principal Investigator and/or Study Physician.