This study defines the goods and services that constitute environmental protection activities in the United States. The U.S. input-output (I-O) table serves as the basis for the definition of envionmental protection activities developed in this study. The U.S. environmental protection input-output tables identify the sectors that receive the revenues associated with that demand enviornmental protection goods and services. The input-output framework also allows for the development of a measure of the importance of enviornmental protection activities relative to the U.S. economy. Finally, employment associated with environmental protection activities can be estimated.