When discussing the drug, the bug, and the host in the past, emphasis was laid mainly upon the interaction between antibiotics and bacteria or the reaction of the host to the invading organism. Today, however, standardized immunologic parameters are available for evaluating cellular and humoral responses and an increasing number of publications deal with the host reaction to the antibiotics administered. Some researchers and clinicians felt that the time had come to bring together investigators studying the influence of antibiotics on the host-parasite­ relationship. The first section of this book therefore covers the influence of chemotherapy on the host defense system. Here antibody production and cellular immunity, the influence of antibiotics on the function of phagocytic cells, and immunostimulation combined with antibiotics in the treatment of infection are presented. The second section deals with the influence of antibiotics on the production of extracellular and cellular virulence factors by bacteria, the adherence of bacteria being of utmost importance here. In addition, phagocytosis and serum bactericidal activity are discussed. In Prof. Opferkuch and Prof. Hahn I found two colleagues keen and knowledgeable enough to organize the First International Meeting on the Influence of Antibiotics on the Host-Parasite-Relationship. These proceedings of the meeting constitute a survey of the latest developments in this field, and should be of interest to clinical and researchers. Bielefeld, September 1982 Hans-Udo Eickenberg Berlin Helmut Hahn Bochum Wolfgang Opferkuch Contents Introduction H. -U.