We have shown that smoking caused first acute myocardial infarction to occur significantly more prematurely in women than in men, implying that twice as many years were lost by women smokers as by men smokers.In smoking women first myocardial infarction occurred 13.7 years prematurely, whereas the corresponding figure in men was 6.2 years.Smoking incurs a strong additional risk in women.Smoking has been known for many years to be a very important risk factor for myocardial infarction, but it has been debated whether smoking increases the risk of heart disease relatively more in women than in men.Smoking habits have changed markedly in the last few decades with men reducing and women increasing tobacco use.Thus, new studies with recently collected data should contribute to an improved understanding of possible sex differences in this area.