The detailed mortality and morbidity statistics on smoking tend to conceal the overall impact of the habit on health. About 3 million people die each year from smoking in economically developed countries, half of them before the age of 70. Cancers of eight sites are recognized as being caused by smoking--lung cancer almost entirely and the others (upper respiratory, bladder, pancreas, oesophagus, stomach, kidney, leukaemia) to a substantial extent. Six other potentially fatal diseases are also judged to be caused by smoking: respiratory heart disease, chronic obstructive lung disease, stroke, pneumonia, aortic aneurysm and ischaemic heart disease, the most common cause of death in economically developed countries. Non-fatal diseases, such as peripheral vascular disease, cataracts, hip fracture, and periodontal disease, which cause appreciable disability, cost and inconvenience are also caused by smoking. In pregnancy, smoking increases the risk of limb reduction defects, spontaneous abortion, ectopic pregnancy, and low birth weight. While there are some diseases for which smoking shows a protective effect, the 'benefits' of these are negligible in relation to the illness and premature mortality caused by smoking. About 20% of all deaths in developed countries are caused by smoking; an enormous human cost which can be completely avoided.