The subject of acid deposition remains one of the most urgent of our contemporary environmental problems. Research programmes are continually redefming our understanding of cause and effect and hence the continuing need for a timely and authoritative series addressing these issues. This volume seeks to review and defme our contemporary understanding of acid deposition by reference to new international data and as a consequence assist the definition of our future research requirements and policy developments. International contributions to the volume are drawn from the Federal Republic of Germany, the U.S.A., Canada, Brazil, Switzerland, Austria, Israel, France and the United Kingdom. Some of these nations have experienced acid deposition on a regional scale for considerable periods of time; for others the phenomenon is an emerging problem. This collection of papers has been compiled by invitation to eminent members of the acid deposition research community and by selection from a carefully targeted call for papers. It is primarily designed to meet the needs of researchers, lecturers and postgraduate students in environmental disciplines and for environmental policy makers. It is of interest to professionals in related disciplines and essential as a reference text for libraries. The volume is divided into four broad themes: Emissions, chemistry and deposition; Ecosystem effects (freshwater, soils and forest systems); Effects on structural materials; Mitigation, control and management. Each of these sections provides an overview of contemporary understanding, presents new experimental or field evidence and provides guidance for our future research agenda.