The biological mechanisms of nicotine dependence are described, the prevalence of tobacco dependency among those using other mood-altering drugs is examined, and the most efficacious way to address this dependency is discussed. New data on the relationship of smoking addiction to other addictions are examined. Topics include: (1) "Tobacco Smoking and Nicotine Dependence: Biological Basis for Pharmacotherapy from Nicotine to Treatments that Prevent Relapse" (M. S. Gold, M. J. Herkov); (2) "Neuropharmacological Actions of Cigarette Smoke: Brain Monoamine Oxidase B (MAO B) Inhibition" (J. S. Fowler, N. D. Volkow, G. J. Wang, N. Pappas, J. Logan, R. MacGregor, D. Alexoff, A. P. Wolf, D. Warner, R. Cilento, I. Zezulkova); (3) "Cigarette Smoking and Major Depression" (L. S. Covey, A. H. Glassman, F. Stetner); (4) "Caffeine and Nicotine Use in an Addicted Population" (L. R. Hays, D. Farabee, W. Miller); (5) "Comorbid Cigarette and Alcohol Addiction: Epidemiology and Treatment" (N. S. Miller, M. S. Gold); (6) "Tobacco, Alcohol, and Drug Use in a Primary Care Sample: 90-Day Prevalence and Associated Factors" (L. B. Manwell, M. F. Fleming, K. Johnson, K. L. Barry); and (7) "Incorporating Nicotine Dependence into Addiction Treatment" (T. A. Rustin). A "Selective Guide to Current Reference Sources on Topics Discussed in this Issue" (L. K. Morgan) is included. (EMK)