Addiction to nicotine is the most common serious condition in medicine today. This chemical dependency has produced the largest epidemic of disease in this century, an epidemic that is beginning to wane in the United States but which is accelerating in the Third World. Widespread cultural acceptance of tobacco and the malignant fostering of use by cigarette merchants has perpetuated the epidemic. Nicotine regularly causes addiction in its users. This condition is best viewed as a chronic disease with remissions and exacerbations. It is highly amenable to treatment, and primary-care physicians are ideally situated to manage this fascinating condition. Physicians have a larger role to play, as well, in the many opportunities that exist to prevent this condition in the young and to protect non-smokers from tobacco smoke pollution.