1. Introduction (P.H. Nienhuis and A.C. Mathieson). 2. Physical Characteristics of Littoral Ecosystems, with Special Reference to Marine Plants (K. Luning and R. Asmus). Temperature. Light. Water motion and other physical factors. References. 3. Chemical Characteristics of Marine Littoral Ecosystems (W. Schramm). Introduction. Import and export processes and chemical characteristics. The influence of non-biological processes on chemical characteristics. Biological activity and chemical parameters. References. 4. Vertical Distribution (G. Russell). Zonation. The supralittoral zone. The eulittoral zone. The sublittoral zone. Causes of zonation. References. 5. Shoreline Ecology in Iceland, with Special Emphasis on the Benthic Algal Vegetation (I.M. Munda). Introduction. Geological history. Abiotic environmental factors. Vegetation patterns and species distribution. References. 6. The Baltic Sea Gradient (I. Willentinus). Introduction. A brief qualitative description of the littoral ecosystem. Communities on rocky substrates. Littoral communities on sandy and muddy substrates. Biomass distribution. Functional aspects of the littoral system. Acknowledgements. References. 7. Northwest Atlantic Rocky Shore Ecology (A.C. Mathieson, C.A. Penniman and L.G. Harris). Introduction. Abiotic environment. Biogeography. Community patterns of open coastal rocky ecosystems: littoral and sublittoral zones. Organization of open coastal rocky ecosystems: littoral and sublittoral zones. Primary productivity of benthic communities. Appendix I: Gulf of Maine. Appendix II: Bay of Fundy. Appendix III: Atlantic coast of Nova Scotia. Appendix IV: Gulf of St. Lawrence. Appendix V: Newfoundland. Acknowledgement. References. 8. Littoral and Intertidal Systems in the Mid-Atlantic Coast of the United States (R.J. Orth, K.L. Heck Jr. and R.J. Diaz). Introduction. Physical setting and sediments. Environmental variables. Faunal and floral characteristics. Functional relations. Acknowledgement. References. 9. The Tropical Western Atlantic Including the Caribbean Sea (C.J. Dawes, E.D. McCoy and K.L. Heck, Jr.). Introduction. Physical Characteristics. Floristic Studies. Faunistic Studies. Communities. Photosynthesis and productivity. Grazing and food webs. References. 10. Open Coast Intertidal and Shallow Subtidal Ecosystems of the Northeast Pacific (M.S. Foster, A.P. De Vogelaere, J.S. Oliver, J.S. Pearse and C. Harrold). Introduction. Abiotic environment. Biogeography. Open coast rocky intertidal ecosystems. Rocky subtidal ecosystems. Sandy intertidal and subtidal beaches. Energetics and trophic relationships. Acknowledgement. References. 11. Southern California Rocky Intertidal Ecosystems (M.M. Littler, D.S. Littler, S.N. Murray and R.S. Seapy). Introduction. Community composition and structure. Primary productivity and functional form relationships. Energetic and food-web relationships. Environmental aspects. Human influences. References. 12.