Book excerpt: Assuming that the complex phenomena underlying the operation of the immune system may be better understood through the collaborative efforts of theorists and experimentalists viewing the same phenomena in different ways, the Sante Fe Institute and the Theoretical Division of Los Alamos National Laboratory cosponsored a workshop entitled "Theoretical Immunology." The workshop focused on themes spanning the field of immunology, with emphasis on areas where the theorists have made the most progress. This book covers the discussions a that workshop on the topics of immune surveillance, mathematical models of HIV infection, complexities of antigen-antibody systems, immune suppression and tolerance, and idiotypie networks. In each of these areas there is reason to believe that advances can be madeeither through interactions among experimentalists and theorists or through the critical look experimentalists and theorists will bring to bear upon one another's work.