The purpose of this study is to determine whether labetalol, an alpha and beta adrenergic blocker, will block the subjective and physiological effects of intravenously administered nicotine in humans. A total of 12 subjects will participate in the double blind placebo controlled, outpatient study. Subjects will have 3 separate experimental sessions 3-9 days apart. On each of the experimental sessions, a single oral dose of low (100mg) or high dose of labetalol (200mg ), or placebo will be administered. Two hours after labetalol or placebo treatment, subjects will receive 15 variance grams nicotine base/kg intravenously. Several physiological endocrine and subjective measures will be obtained during the sessions. We propose that blockage of adrenergic receptors by labetalol will significantly block the physological and subjective effects of nicotine.