Week 1 to 12 visits Subjects will return for visits to the clinic after the baseline visit over the following 12 weeks at Weeks 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. Subsequent to Week 1 Target Quit Date (TQD-visit), visits will occur within 3 days of each scheduled visit date. The subjects will attempt to quit on the target quit date at the Week 1 visit. The quit attempt should occur in the morning prior to the clinic visit that day, so that the subject's last cigarette prior to the quit attempt will be before midnight the night prior to the Week 1 visit. Subjects will be called 3 days after the target quit date (TQD+3) to be reminded of study participation and to receive support for the smoking cessation attempt. These contacts should be no longer than 5 minutes and counselling will follow AHRQ guidelines. Activities to be carried out during these visits are detailed in the Appendix A. At each visit, participants will be provided approximately. 10 minutes of counselling. Study drug will be dispensed by qualified personnel according to the plan illustrated in the Appendix A. Any unused study drug must be returned to the clinic at each visit or upon early termination. All subjects will complete the treatment phase after 12 weeks of participation. Following completion of the Week 12 visit, subjects will continue in the nontreatment follow-up phase of the protocol (see Appendix B). Subjects who do not complete the Week 12 visit will not be eligible to continue. If a subject discontinues study drug prior to the Week 12 visit, the subject may continue study participation as long as they complete the remaining scheduled visits through Week 12. Only subjects completing the week 12 visit will be eligible to continue in the nontreatment follow-up phase of the protocol.