Smoking is the inhalation and exhalation of the fumes of burning tobacco. Tobacco leaves are dried and cured, then rolled into cigars or shredded for pipes or cigarettes, the most popular method of smoking. About 50 million people in the United States smoke a total of 570 billion cigarettes each year.

In the 1940s, smoking was considered harmless, but laboratory and clinical research has since proved that cigarette smoke contains around 4000 chemicals, some of which are highly toxic. Nicotine, a major ingredient of tobacco smoke, is very addictive. Cigarettes may be responsible for up to 419,000 deaths per year in the United States. According to the American Cancer Society, smoking is the most preventable cause of death in America today. Tobacco smoking in the United States may be about 20 times the mortality due to all other addictive drugs combined.

Smoking increases the risk of cancer of the lung, larynx, oral cavity, esophagus, bladder, kidney, and pancreas, as well as the risks of chronic bronchitis, emphysema, and stroke. Smokers more frequently give birth to premature or underweight babies. Risks are also increased by environmental tobacco smoke when nonsmokers must share the same environment as a smoker. The smoking habit and addiction to nicotine usually begin at an early age. In the United States, more than 70 percent of adults who smoke began smoking before the age of 18.

Tobacco was first smoked by Native Americans before contact with Europeans. Europeans took the custom to their native lands, where it became popular. The general attitude of society was that smoking relieved tensions and produced no ill effects. As cigarette consumption increased dramatically in the United States and some European countries, epidemiologists noticed a link between smoking and the incidence of lung cancer, which increased a lot around 1930. The 1964 U.S. Surgeon General's report labeled smoking a health hazard, and millions of Americans quit. Smoking in adults began to go down after the 1964 report, but numbers have leveled off after falling about 40 percent.

Attitude against smoking has grown in the United States, despite the resistance of tobacco companies. It is now illegal to smoke in federal and many state buildings and on most domestic airline flights. Advertising of tobacco products has been banned from radio and television since 1971, and health warnings are required on cigarette packages. In the largest class action suit ever filed, a major tobacco consortium agreed in 1996 to compensate five states for costs incurred in the treatment of individuals who claimed to be addicted to tobacco products.

Books, pamphlets, and group help are used to help quit smoking. Devices such as nicotine patches and nicotine gum help reduce the craving for cigarette smoke. Benefits of quitting include immediate reduction of health risks and lower health insurance payments.