When writing about "the second epidemiologic revolution," Terris discussed 2 eras in health. The first era-the communicable disease era-began during ancient times and continues today; the second era-the chronic disease era-began during the 20th century, particularly among the industrialized nations. Although neither revolution against these types of diseases is complete, we have made such considerable progress that substantial and growing segments of the population no longer regard disease as the only, or even the primary, health problem. Increasingly, the goal is a long and fruitful life, not simply the absence of disease. That potential and the effort to achieve it compose the third era of health, and a proposed new measure of health is outlined in this article.