Smoking can cause a variety of cancers, cardiovascular disorders, and other health problems. Quitting smoking greatly decreases one's risk for these problems. Studies have shown, however, that quitting smoking is more difficult for women than men. Despite that knowledge, little research has been done to try to understand the mechanistic differences between men and women that may cause this distinction. This study will assess whether the reduced effectiveness of nicotine replacement therapy in women is caused by physical and psychological gender differences in the withdrawal suppression induced by nicotine replacement therapy.