Foreword. Session A. Opening session. Acidification: an international problem (J.G.M. Alders). Acidification as an example of the link between science and policy (G.J.R. Wolters, H. Marseille). Acidification research and policy in the province Limburg (H.W. Riem, B.R. Pasma, D. van Nierop). Session B. State-of-the-art of acidification research. Forest vegetation and acidification: a critical review (R. Schlaepfer). Global environmental change: implications for acid deposition research (D.J. Waters, P.G. Whitehead). The role of ammonia in acidification: perspective for the prevention and reduction of emissions from livestock operations (A.A. Jongebreur, J.H. Voorburg). Emissions of acidifying components (M. Amann). Acidification of forests and forest soils: current status (E. Matzner). Stress combinations in forests (J.L. Innes). Effects of increasing nitrogen deposition and acidification on heathlands (J.A. Lee, S.J.M. Caporn, D.J. Read). The interaction of forest vegetation and soils with the aquatic environment; effects of catchment liming on lakes (T.R.K. Dalziel, G. Howells, R.A. Skeffington). Higher order effects (L. Reijnders). Acidifying effects on groundwater (J. Soveri). Monitoring for the future: integrated biogeochemical cycles in representative catchments (T. Paces). The critical loads concept for the control of acidification (J.-P. Hettelingh, R.J. Downing, P.A.M. de Smet). Session C. Acidification policy. Canadian acid rain policy (S.Milburn-Hopwood, K.J. Puckett). Acidification policy in Finland (E. Lumme). Acidification policy - control of acidifying emissions in Germany (B. Schärer). Acidification policy in Hungary (E. Kovács). Acidfication abatement policy — The Netherlands experience (G.J.A. Al, V.G. Keizer). The convention on long-range transboundary air pollution: its achievements and its potential (H. Wüster). Acidification policy — Sweden (K. Lövgren, G. Persson, E. Thörnelöf). Air pollution control policy in Switzerland (B.C. Gälli Purghart). Acidification research: evaluation and policy applications; a United Kingdom policy response (R.G. Derwent, R.B. Wilson). Acidification policy in the United States (D. Leaf). Session D. New research results on the acidification problem. Setting priorities for the measurement of acid aerosols and gases: 3 examples for Switzerland (P.A. Alean-Kirkpatric, J. Hertz). High resolution assessment of acid deposition fluxes (W.A.J. van Pul et al.). Measuring and modelling atmospheric dry deposition in complex forest terrain (G.P.J. Draaijers et al.). The transplantation of four species of Lobaria lichens to demonstrate a field acid rain effect (A.M. Farmer, J.W. Bates, J.N.B. Bell). Acidification research activities in Poland (W.A. Mill). Critical loads for Dutch forest soils (W. de Vries et al.). Scenario analysis with the Dutch Acidification Systems (DAS) model; an example for forests and forest soils (A. Tiktak et al.). Acid rain abatement in Belgium: lessons of cost-effectiveness studies (C. Cuijpers, S. Proost). Base content in soil and problems arising in connection with acidification (L. Werner). Measurements of tree growth and health in the Liphook Forest Fumigation project: an evaluation of large scale open air fumigation experiments (M.R. Holland, P.W. Mueller). Session E. Results from national research programmes. The United States national acid precipitation assessment program (P.M. Irving). The United Kingdom research programme and its implications for policy, now and in the future (R.B. Wilson). Research into forest decline and air pollution in France; major findings and relevance for policy applications (G. Landmann). Background, results and conclusions of the Dutch Priority Programme on Acidification (G.J. Heij, T. Schneider). Acidification research in Sweden (H. Staaf, U. Bertills). Finnish research program on acidification (HAPRO) 1985-1990 (P.E. Kauppi). Status of acidification research in Czechoslovakia and its relationship to politics and economics in Europe (T. Paces). The Swiss national research program "Forest Damage and Air Pollution" (F. Haemmerli, N. Kräuchi, M. Stark). Session F. Closing session. A comparison of some national assessments (J. Nilsson, E. Cowling). Poster Session. List of Participants.