Tobacco is still widely consumed in a variety of different ways, mainly as smokeless tobacco and cigarette smoking. Four traits characterize tobacco use whatever the way of using it: 1) addiction linked to nicotine is behind all the tobacco hazards; 2) individual variation in tobacco susceptibility; 3) dose-response relationship; 4) time-lag effect. Smokeless tobacco, chewed or snuffed can lead mainly to inflammation of the oral cavity and oral cancers. Cigarette smoking accounts for 65-85% of global tobacco consumption. Active smoking can cause: 1) respiratory disorders culminating in chronic obstructive pulmonary disease (COPD) and emphysema; 2) cardiovascular hazards by way of increased vascular spasm and atherosclerosis leading to acute and chronic myocardial events, cerebral and peripheral vascular diseases; 3) cancers: twelve types are caused or related to cigarette smoking. Lung cancer is still the leading cause of cancer death in most high-income countries where data are available. An excess mortality is associated with smoking, with a 2-fold greater risk in smokers than in nonsmokers throughout middle age. The exposed pregnant woman subjects herself and her pregnancy to risks, and her fetus to growth retardation and perinatal morbidity and mortality. Passive smoking implicates 20-80% of the whole population. It can be nearly as harmful as active smoking depending upon risk factors, and can lead to short as well as to long-term effects. Children are the most vulnerable population particularly during the first years of life. Passive smoking increases risks for higher and lower respiratory tract illness but a smoke-free environment improves all these disorders. Ischemic heart diseases and lung cancer are the main risks for non smoking adults exposed to cigarette smoke. Tobacco use and exposure is the single most important source of preventable morbidity, disability and premature mortality. But giving up smoking helps at any time, the sooner the better. Health professionals should be the key advocates in tobacco prevention.