This book collects together a selection of the best papers presented at the Third International Bioastronomy Symposium held in 1990. The subject is bioastronomy, the search for life in the universe, andthe book is devided according to the five main stages of life as recognized by this new branch of science: cosmic organic, prebiotic, primitive biological, and advanced. Thereader will find here the most recent results obtained by top specialists from all over the world on hot topics such as the formation and discovery of planets, organic chemistry in meteorites and comets, prebiotic chemistry...