The Montreal Process was formed in 1994 to develop an internationally agreed upon set of criteria and indicators for the conservation and sustainable management of temperate and boreal forests (Anonymous 1995). In response, the Forest Inventory and Analysis (FIA) and Forest Health Monitoring (FHM) programs of the U.S. Forest Service implemented a national ozone (O3) biomonitoring program to address specific questions about the area and percent of forest land subject to levels of O3 pollution that may negatively affect the forest ecosystem. This is the first and only nationally consistent effort to monitor O3 stress on the forests of the United States. This program provides critical baseline information on the current status of O3 air quality and the potential effects of O3 on forest health and productivity.