There has been considerable advancement in the understanding of the S biogeochemistry of forested ecosystems. Many recent studies have focused on ascertaining the impacts of acidic deposition of forest vegetation, soils and surface waters. Sulfur dynamics effects the flux of both H(+) and SO4(2-) both of which interact with other elemental cycles especially N and basic cations. There is extensive information on the S constituents and fluxes for temperate forest ecosystems, but little for tropical areas. These latter areas may be particularly important contributors to trace S gases in the troposphere. On regional as well as global scales, forest ecosystems are being subjected to changes in atmospheric loadings of S as well as other anthropogenic effects including deforestation and climatic alterations. Predicting how these changes will be, affect both organic and inorganic S pools of forest ecosystems and how these alterations will influence gaseous and leaching losses should be the general focus of future research on S biogeochemistry.