The concept of smoking has evolved considerably in recent decades. From a habit in the 1960s, tobacco consumption came to be viewed as a chemical dependency in the 1970s and an addiction in the 1980s, until smokers' clinics were implemented in the 1990s. To understand the mechanism of the smoking habit, it is important to recall that smoking represents much more than physical dependence on nicotine. Over time, smokers receive social, behavioral, and cultural stimuli that reinforce their habit and probably serve as the causal elements for establishing their psychological dependence. Both the psychological and physical components of tobacco dependence play a fundamental role in maintaining the habit.