 Participants will be randomly assigned to abstain from all nicotine use for 7, 14, or 35 days and participate in one cue-reactivity session on day on the last day of abstinence groups 1, 2, and 3a; N50 per condition. The cue-presentation task will involve visual, olfactory, and tactile cues. After cue presentation, participants will complete the Brief Questionnaire of Smoking Urges and other standardized mood questionnaires. Physiological responses and auditory reaction time will be obtained. Group 3b N40 will also abstain for 35 days, but will complete the cue-reactivity task two additional times to provide a within-study examination of the changes in cue reactivity over long periods of abstinence. On each laboratory visit, participants will give a urine sample to be tested for cotinine and a breath sample to be tested for carbon monoxide CO to verify abstinence from smoking. Participants will receive 20 in cash if both tests are negative, and they will accumulate a further 10 to be paid as a bonus at the end of the abstinence phase. After their required abstinence period of 7, 14, or 35 days, participants will enter a five-day step-down period during which they will continue to report to the laboratory for 10 min a day, and they will receive payments for abstinence in descending value across days. One of the primary outcome measures in the study is the time to return to smoking, beginning from the last day of required abstinence. After the step-down period, for the final 12 days of the study, volunteers will report to the lab every 3 days to give urine and breath samples and to report the number of cigarettes smoked. Participants will receive 15 for each visit to the laboratory, and they will receive an end-of-study bonus of 25 for attending all visits. This money will be paid regardless of whether they abstain from smoking. 