Increasing interest in the immunology of mucosal surfaces is obvious from the number of publications in scientific journals and from the frequency of national and international symposia devoted to this subject. Particularly encouraging are the large numbers of young investigators who have chosen to work in this area of theoretical immunology with profound practical implications. The two volumes represented here are the result of an International Congress Of Mucosal Immunology held at the Niagara Falls Convention Center and the Niagara Falls Hilton on June 29 - July 3, 1986. This satellite meeting of the International Congress of Immunology placed emphasis on all aspects of the Mucosal Immune System. This included the regulation of differentiation of mucosal lymphocytes, mucosa-associated lymphoreticular tissue and lymphocyte homing, the immunology of mucosa associated tissues and glands, effector functions in mucosal immunity, and the effects of environmental antigens on the immune response, all of which are included in Volume I. The second volume has emphasized studies of the immune response and effector functions, IgA biosynthesis and transport, IgA proteases and effector functions, developmental aspects and immunodeficiency, the immunopathology of IgA and mucosal immunoprophylaxis. A total of 218 papers are included in these two volumes and a comparison to past meetings held at four to five year intervals indicates the explosive growth of mucosal immunology.