This volume represents the Proceedings of the World Conference on Embryo Transfer, In Vitro Fertilization and Instrumental Insemination held on September 24-27, 1980 in Kiel, West Germany. Professor Dr. L. Mettler and Dr. H. H. Riedel of Frauenklinik der UniversiUit in Kiel were the local co- chairpersons, who contributed very richly to the program. Basic research, clinical trials, preparation of manuscripts, editorial assistance and presentation of results were generously supported by the following institutions and organizations: Kulturministerium des Landes Schleswig-Holstein Medizinische FakuItat der Christian-Albrechts-UniversiUit, Kiel Wayne State University School of Medicine; Detroit, Michigan, USA C. S. Mott Center for Human Growth and Development; Detroit, Michigan, USA Universitats-Frauenklinik und Hebammenlehranstalt; Kiel, West Germany Serono GmbH; Freiburg, West Germany Hutzel Hospital; Detroit Medical Center; Detroit, Michigan, USA Deutsche Gesellschaft fUr Gynaekologie und Geburtshilfe; West Germany Deutsche Gessellschaft zum Studium der Fertilitat und Sterilitat; Sektion Andrologie Thanks are also due to Aponti GmbH (5000 Koln 21), Bayropharm GmbH (5000 Koln 80), Deutsche Lufthansa (5000 Koln), Organon GmbH (8024 Oberschleissheim), Winthrop GmbH (6080 New Isenburg), and Wisap GmbH (8029 Sauerlach), for financial assistance. Sincere appreciation and gratitude are due to the contributors who meticulously prepared their chapters; to Ms Jackie Mucci for editorial skills and assistance, and Ms. Jackie Smieska for editorial help. Thanks are also due to Dr. H. D. Brackebusch for his assistance during the conference; to Ms. E. Seiss for her secretarial assistance; and to Mr.