Tobacco dependence prevents any reduction in morbidity and mortality related to smoking. Nicotine is widely regarded as responsible for this dependence process. It stimulates ubiquitous cholinergic receptors thus resulting mainly in catecholamine release. The causal role of nicotine in inducing and maintaining tobacco dependence is not so obvious as that of drugs responsible for other addictions. Animal models that have been described are not convincing. Smokers tend to change their smoking patterns so as to keep blood nicotine levels constant when nicotine yields of cigarettes are manipulated. This "nicotine titration phenomenon" is a strong argument in favor of them craving for nicotine. However, other components, such as tar, vary correlatively. Nicotine gum helps to quit smoking, but few people become gum-addicted. A better knowledge of the tobacco components that may induce dependence is needed to understand its neurochemical mechanisms and to provide the tobacco industry with adequate information for manufacturing less hazardous products.