Cardiovascular diseases comprise especially the major disorders of the heart and the arterial circulation supplying the heart, brain, and peripheral tissues. Their common occurrence in most populations and the great attendant mortality, loss of independence, impaired quality of life, and social and economic costs are compelling reasons for public health concern. The epidemiology and prevention of these diseases involve the understanding of their causes, identification of means of prevention, and monitoring of populations to assess the changing burden of these diseases and the measurable impact of interventions to control them. Together, the cardiovascular or circulatory diseases have figured prominently in the large shifts among causes of death, especially in industrial societies, during the 20th century. During this period they have become the predominant cause of death in many countries and in the world as a whole. The “theory of epidemiologic transition” offers an interpretation of these shifts. It may have special implications for developing countries, as increasing proportions of these populations attain older ages, social changes unfold, and disease patterns change. Evidence indicates that cardiovascular diseases are already epidemic in low- and middle-income as well as high-income regions of the world and have become deep-rooted in most societies in recent decades.