The pursuit of health has become a highly valued activity in modern and contemporary life, commanding enormous resources and generating an expansive professionalization and commercialization along with attendant goods, services and knowledge. Health has also become a focal, signifying practice. As a 'key word', health is constructed in relation to social structures and experience and systematically articulated with other meanings and practices. Although the cogency of health as a practical concept is largely a product of the enormous influence of modern medicine, medical conceptions have never been able to contain the irrepressible proliferation of meanings associated with health. The meaningful - and ideological - practices of health can be illustrated by comparing three periods in American culture: (1) the late 19th and early 20th century; (2) the 1970s and 1980s; and (3) the first years of the 21st century.