experimental verification of GUTs has led to valiant experimental efforts in recent years to observe nucleon decay in massive underground detectors. Experiments to search for superheavy monopoles may eventually require similar efforts. Since the unification scale is unreachable in the laboratory, monopole detectors must search for relics of the big bang. Much theoretical groundwork has been accomplished in recent years with the development of GUTs. In Part I of this book, Erick Weinberg gives a theoretical overview of the role of magnetic monopoles in the various unification schemes. Monopoles in the context of the newly revived Kaluza- Klein theories are presented by several authors and are summarized by Qaisar Shafi. Mike Turner begins Part II with a discussion of monopoles in standard big bang cosmology. Paul Steinhardt follows with his perspectives on the inflationary universe; C.