Following increases up until the late 1980s, some decline in cancer mortality has been observed in North America and in Western Europe. Approximately half the decline can be attributed to the levelling off in lung and other tobacco-related cancer epidemics and the rest to several factors, including reduced exposure to occupational carcinogens, prevention and early diagnosis, and improved treatment. Between 25 and 30% of all cancer deaths in Europe are due to tobacco smoking. In this review the effect of tobacco smoking on cancer incidence and mortality is examined, together with other important aetiological factors including alcohol, diet and environmental and occupational carcinogens. The effect of new treatments and the potential for prevention of cancer are also discussed.