In industrialised countries, lung cancer is the most common form of cancer among males and it is growing among females. For both sexes, rates reflect smoking behaviours. The pattern appears to be different in Asia, particularly in China, where lung cancer rates in men reflect high smoking rates but high rates among non-smoking women appear to be related to other factors. The incidence of lung cancer is low in most African countries, but it is increasing. In addition to tobacco smoking, a number of etiological factors have been identified for lung cancer: indoor exposure to environmental tobacco smoke, cooking oil vapour, coal burning, or radon, outdoor air pollution and occupational exposure to asbestos and other carcinogens. Recent studies have shown that dietary factors may be important, with high consumption of vegetables and fruits being protective while preserved food and fatty food are harmful, and certain infections such as Mycobacterium tuberculosis, human papilloma virus and Microsporum canis are associated with a high risk of lung cancer. Among non-smokers, the probable role of genetic predisposition in lung cancer by increasing the individual's susceptibility to environmental carcinogens is currently being studied actively. As the single most important cause for lung cancer is tobacco smoke and, with increased sales, a major epidemic is predicted for both Asia and Africa, all health care professionals, government health authorities and national and international health organisations must join in a concerted effort against tobacco.