The International Seminar on Modern Aspects of Microbiological Hydrometallurgy held in Moscow on June 21-26, 1982 was attended by the Course trainees and internationally reputed scientists in this field who presented papers on recent research advances in biogeo-technology. This volume comprises both papers presented at the International Seminar and lectures, in a revised form, delivered at the International Training Course. Presentations included in this volume cover a wide spectrum of microbiological and technological problems related to the use of bacteria in biogeotechnology as well as their role in geochemical processes.