Recent events in the United States have generated significant negative publicity relative to smoking, nicotine, and the people who use tobacco products. Despite the renewed interest in these areas and the flurry of activity surrounding smoking, the question 'Why do people smoke?' still remains largely a matter of debate. The 'simple' answer to this question offered by the anti-smoking community and legitimized by the 1988 US Surgeon General's Report is that people smoke because they are 'addicted' to nicotine, through the same mechanisms that determine addiction to heroin and cocaine. The arguments used to support this position clearly do not stand-up to scientific scrutiny (Robinson & Pritchard, Psychopharmacology, 108, 1992, 397-407). The present paper will summarize the scientific data with regard to nicotine 'addiction', demonstrating that behavioral intoxication is a key component of any meaningful definition of addiction, and that nicotine absorbed from tobacco smoke does not impair psychological or motor functioning. In response to the Surgeon General, it will be argued that the physiologic, pharmacologic and behavioral effects of nicotine absorbed from smoke are fundamentally different from the effects of addicting drugs such as heroin and cocaine, and more similar to the effects of caffeine absorbed from coffee. If people are not 'addicted' to tobacco smoke, what is the source of the pleasure associated with smoking? Obviously, the sensory aspects of smoke play an important role in both the pleasure associated with smoking and the smoker's brand selection. In addition, data from scientific studies have shown that smoking is associated with a wide variety of positive effects on mood and mental performance that may play a role in reinforcing the smoking habit. Data will be reviewed demonstrating that smokers achieve personal benefits from smoking in the areas of stress reduction, faster reaction times, increased efficiency of information processing, and an enhanced ability to sustain attention. In addition, smoking seems to facilitate learning as well as skills associated with automobile driving. These scientific data offer an alternative explanation to the 'addiction' hypothesis and argue that people smoke not because they are addicted, but because smokers find smoking a pleasurable activity with well-defined emotional and cognitive benefits.Finally, recent epidemiological and pharmacological evidence suggests that smoking/nicotine may delay or prevent certain diseases of the central nervous system (CNS). These benefits probably do not help answer the question 'Why do people smoke?', but they do open exciting new vistas for nicotine related research. The data supporting the negative associations between smoking and Alzheimer's and Parkinson's diseases and ulcerative colitis will be summarized as well as the pharmacologic evidence that supports a therapeutic role for nicotine in the treatment of these diseases.