These proceedings present the most up-to-date information on the interrelations between microorganisms and plants in the rhizosphere, and the possibility of utilizing these relationships to improve plant growth, health and yields. The application of some biological preparations may in the future partially replace the use of agrochemicals and thus contribute to environmental improvement and enhancement of the quality of soil, water and foodstuffs. The Symposium brought together specialists from fifteen countries to assess the advances in a field which has recently attracted considerable interest and is also important for society at large. The book contains over sixty contributions from rhizosphere microbiologists, focusing on the study of the function of microorganisms in the root system of crop plants and in its immediate vicinity, the effect of the plants themselves on this function, the interrelationships among different microorganisms in the rhizosphere and the elucidation of the mechanisms of microbial action in the agroecosystem. All these lines of research are intimately associated with the problems of soil fertility and crop yields, which in turn have a direct bearing on the nutrition of mankind and on environmental protection. The papers have been divided into four topics: symbiotic microorganisms in the root system; associative microorganisms in the root system; soil-borne phytopathogenic and phytotoxic microorganisms; and microbial preparations stimulating growth and improving the plant health. Each section starts with invited lectures from outstanding specialists. The work includes numerous tables, figures and references. The volume is primarily directed at soil microbiologists, plant pathologists and physiologists, ecologists as well as specialists in agronomy and environmental protection.