In 1971 the International Society of Tropical Ecology and the International Association for Ecology held a meeting on Tropical Ecology, with an emphasis on organic production in New Delhi, India. At this meeting a Working Group on Tropical Ecology was organized, consisting of K. C. Misra (India), F. Malaisse (Zaire), E. Medina (Venezuela) and F. Golley (U.S.A.). The object of this Working Group was to stimulate interaction between tropical ecologists through future scientific meetings and other exchanges and communications. A second meeting of ISTE and INTECOL was held in Caracas, Venezuela in 1973, under the direction of Medina and Golley and sponsored by the Depart ment of Ecology, Institute Venezolano Investigaciones Cientificas (lVIC). The basic structure of the meeting was provided by series of invited papers which considered topics of special interest from both an applied and theoretical view. These included physiological ecology (Pannier), populations (Rabinovich), tropical savannas (Lamotte), rivers (Sioli), estuaries (Rodriguez), and island ecosystems (Mueller-Dombois). Contributed papers considered details of these and other ecological topics, including the application of ecology to human problems. The present volume includes the invited papers listed above and a sampling of contributed papers which together illustrate the trends of research in tropical ecology. The papers show that tropical ecology is a vigorous subject of research. While the papers in this volume do not provide reviews of all the topics of study in tropical ecology, they do present authoritative statements on progress in the major subject in the field.