A group of acknowledged experts describe the use of spectroscopy as a diagnostic probe of astronomical environments. The broad sweep of the book enables good coverage to be given to all the situations in which plasmas are encounteres in astronomical investigations. Specifically, the articles include quasars, Seyfert galaxies, active galactic nuclei, the solar chromosphere and corona, galactic HII regions, circumstellar shells, interstellar gas, supernova remnants and interstellar clouds. The book includes an account of the basic aspects of spectroscopy in a chapter on laboratory astrophysics. The book was stimulated by the extraordinary contributions to astronomical spectroscopy of Leo Goldberg, and is dedicated to him. Throughout, this book is written with the needs of students in astronomy and astrophysics in mind. Each chapter includes a summary or conclusions about the future direction of research. Furthermore there are extensive bibliographies. This textbook is therefore an excellent introduction to research in astrophysics and it will act as a pathfinder to the primary literature.