th th On June 17 and 18 1987 the fourth workshop on "Azospi rillum: Genetics, Physiology, Ecology" took place at the Uni ver sity of Bayreuth, West Germany, organized by the Genetics depart ment. There were about 80 participants, who came from German research institutions, from other European countries, from Is rael, Egypt, India, North Vietnam, and North and South America. The former workshops had also taken place in Bayreuth, in 1981, 1983 and 1985, hence the organizers could draw on the experience obtained at these earlier workshops. Azospirilla have, during the past 15 years, found an ever increasing scientific interest because, first, these soil bacte ria carry the genetic information for binding molecular nitrogen from the air and, second, they live in close vicinity to the roots of grain crops and forage grasses. By exploitation of these two properties, it is hoped to develop inoculation procedures which can be used in nitrogen-deficient soils.