This Special Issue of Water, Air, and Soil Pollution offers original contributions from BIOGEOMON, The Third International Symposium on Ecosystem Behavior, which was held on the campus ofVillanova University from June 21-25, 1997. Previous meetings were held in Prague in 1987 and again in 1993. The BIOGEOMON series was initiated in 1987 when a group of researchers from the Czech Geological Survey organized a conference called GEOMON, Geochemical Monitoring in Representative Basins. GEOMON was fairly narrowly focused on monitoring of element pools and fluxes on a small watershed scale. As signalled by the change in name to BIOGEOMON, the second conference explicitly recognized that assessment of anthropogenic effects on ecosystem processes requires a combination of geochemical monitoring with other approaches, including watershed-level manipulations, use of radioactive and stable isotopic tracers, and both empirical and process modeling. The 1997 BIOGEOMON conference was the largest, with over 240 participants from 28 countries on five continents in attendance, and broadest in scope. The conference featured a plenary speaker, six keynote speakers, 35 invited speakers, over 60 oral contributed presentations, and over 75 poster presentations.