Smoking is the leading preventable cause of premature death and disability in Canadian women. Lung cancer, ischemic heart disease, chronic obstructive lung disease, and stroke account for two-thirds or more of the smoking-attributable deaths in women. Lung cancer now exceeds breast cancer as the leading cause of cancer death in women, and both incidence and mortality rates continue to climb. Strong evidence suggests that for the same number of cigarettes smoked, women are more susceptible than men to the carcinogenic effects on their lungs. Evidence also is growing that lung function in women is more adversely affected by smoking and that smoking may be a stronger risk factor for myocardial infarction in women than it is in men. More research into the mechanisms underlying these gender-related susceptibilities is needed. Policies and programs to prevent girls from starting to smoke and to facilitate quitting in women of all ages must be public health priorities.