Cigarette smoking is the major avoidable cause of death and disability in developed countries. Smoking is now increasing fastly throughout the developing world and is one of the biggest threats to current and future world health. For most smokers, quitting smoking is the single most important thing they can do to improve their health. Encouraging smoking cessation is one of the most effective and cost effective things that doctors and other health professionals can do to improve health and prolong their patients' lives. This series will explore the reasons why smokers smoke, how to help them to quit, and how to reduce the prevalence of smoking more generally.

Cigarette smoking first became a mass phenomenon in the United Kingdom and other more affluent countries in the early 20th century after the introduction of cheap, mass produced, manufactured cigarettes. Typically, a "smoking epidemic" in a population develops in four stages: a rise and then decline in smoking prevalence, followed two to three decades later by a similar trend in smoking related diseases. Usually, the uptake and consequent adverse effects of smoking occur earlier and to a greater degree among men. In the United Kingdom there are about 13 million smokers, and worldwide an estimated 1.2 billion. Half of these smokers will die prematurely of a disease caused by their smoking, losing an average of eight years of life; this currently represents four million smokers each year worldwide. Deaths from smoking are projected to increase to more than 10 million a year by 2030, by which time 70% of deaths will be in developing countries.