Environmental tobacco smoke is a recognized factor of morbidity and mortality. The first victims are children, sometimes starting from conception, but adults are not spared. In practice, evaluation of exposure to tobacco smoke can be achieved with more or less specific markers of tobacco smoke.Exposure of the fetus to maternal smoking and of the infant to environmental smoke can have a serious sometimes life-threatening impact. Such exposure increases the risk of spontaneous abortion, ectopic pregnancy, intrauterine growth retardation, premature membrane rupture, preterm birth, retroplacental hematoma, placenta praevia, and sudden infant death. Adult respiratory and cardiovascular disease are also influenced by environmental smoke. In France passive smoking causes premature death of 3000 persons per year.Better knowledge of the risks of exposure to passive smoking can facilitate application of legislation with the objective of protecting non-smokers.Rigorous application of current legislation is important to achieve the stated goals of prevention of smoking as well as assistance to cease smoking.