This book contains lectures presented by outstanding mathematicians and mathematical physicists at the NATO Advanced Research Workshop on noncompact Lie groups held in San Antonio, Texas in January 1993. It touches almost every important topics in the modern theory of representations of noncompact Lie groups and Lie algebras, Lie supergroups and Lie superalgebras, and quantum groups. It also includes several of the applications of this theory. The articles are exceptionally well written, ranging from expository articles easily accessible to graduate students to research articles for specialists which provide the most recent developments in this field -- some of which are being published for the first time here. The book also provides a coherent and readable introduction which reviews the underlying theory and defines the fundamental and relevant terms for the reader. The text is an outstanding source of material for mathematicians and mathematical physicists who are working or are planning to work in the field of representation theories of Lie groups, Lie supergroups and quantum groups. <br/>