Interested smokers phoned a central research office, where they completed a telephone screen to determine eligibility. Participants who passed the telephone screen were invited to an informational session where they provided written informed consent. Next, participants completed three in-person baseline sessions. During the first baseline session, participants underwent further screening including collection of relevant medical history information, vital signs measurements, and a carbon monoxide (CO) breath test. Additionally, at this visit, participants completed several demographic, smoking history, and tobacco dependence questionnaires.
