Over the past 20 years, a new scientific discipline based on direct measurement of human exposure to environmental pollutants has developed. The fundamental principle of the new science is to ''measure where the people are.'' This has required developing small, lightweight, quiet personal monitors for volatile organic compounds and other pollutants. A second principle has been to measure body burden, particularly exhaled breath, whenever possible to determine the relationship between exposure and dose. Studies employing the new monitors and breath measurements have overturned accepted ideas about the sources of most volatile organic pollutants. The main sources turn out surprisingly often to be small, close to the person, and completely unregulated. These findings should result in major changes in our approach to environmental regulation; however, powerful forces of resistance would need to be overcome.