 This study will examine the effect of combining prolonged exposure, a cognitive-behavioral treatment program for post-traumatic stress disorder PTSD with medication varenicline and counseling treatments for smoking cessation. Subjects will be randomly assigned to a 3-month treatment of either: 1 varenicline and smoking cessation counseling alone, or 2 prolonged exposure, varenicline, and smoking cessation counseling. Assessments will be completed at the end of treatment and 6-month follow-up. 