When comparing the number of contributions for the proceedings of the third symposium on The Influence of Antibiotics on the Host-Parasite Relationship with those of its two predecessors, one becomes aware of the progress that has been made in this field. It is obvious that the design of experiments has substantially refined and therefore the clinical relevance of the results has gained in significance. The editors of this volume would like to thank all the colleagues who contributed to this book. It is hoped that interest in this field will develop further and that it will finally yield results which one day may be the basis