This self-contained introduction to molecular astrophysics is an excellent summary of present knowledge and outstanding questions, one that will be valued by scientists who wish to become familiar with this field. The contributors describe the distributions and types of molecules observed in galactic and extragalactic sources, including those in the vicinity of diffuse and dense clouds. In addition, chemical reactions in shocks and dynamically evolving clouds are considered. This is a highly suitable text for astrophysicists, physical chemists, atomic and molecular physicists, atmospheric scientists, and students in advanced postgraduate courses on interstellar matter.