In keeping with the research mission of the Trudeau Institute, the meeting in July 1985 dealt with understanding the immune response to infectious agents, tumors, and allografts. Its major purpose was to provide for interactions among researchers actively engaged in the study of immunology at cellular, molecular, and physiologic levels. As is evident in this volume, the meeting participants considered the composition and function of lymphoid and mononuclear phagocyte systems and the response of the host to several important antigens as measured in vitro and in situ. The lymphocyte cell surface and the function of cytokines were the main molecular subjects of the meeting.