The overall objective of this project is to gain knowledge that will be useful in the development of rationally based treatment strategies for assisting smokers to abstain from cigarettes. Cigarette smoking is the major cause of lung cancer and a major contributor to cardiovascular disease. Specifically, this project tests the hypothesis that two primary factors, nicotine addiction and self-medication, are responsible for smoking motivation and for relapse to smoking after a period of abstinence. Addiction is hypothesized to be related to relief from nicotine withdrawal symptoms, while the need for self-medication arises from basic dysfunctions in personality or temperament. It is hypothesized that a given smoker may be high or low on either or both of these factors and that being high on either of them will be associated with a high rate of relapse subsequent to quitting smoking. The validity of this hypothesized smoker typology as well as three specific program goals will be assessed. 1) the assessment of individual differences in psychological and physiological responses (heart rate, skin temperature, EMG, and left and right hemisphere EEg activity) to quantified doses of nicotine; 2) the assessment of individual differences in physiological and psychological responses to short-, intermediate-, and long-term smoking cessation; 3) the testing of specific hypotheses relating smoking relapse to individual differences in: physiological activity, during resting and stressful conditions; physiological and subjective responses to nicotine and nicotine withdrawal; pre-cessation salivary cotinine concentrations; smoking history; self report indices of personality, smoking motivation, and tolerance. Studying the effects of smoking cessation over time will help us understand the biological and psychological mechanisms associated with smoking relapse. This is important because approximately two-thirds of chronic smokers who attempt to quit smoking relapse within one year. It is expected that knowledge gained from this research will lead to the development of new techniques for helping smokers to quit smoking permanently.