The purpose of this volume, the proceedings of the Second Ovarian Workshop, is to review the state of the art in, the field of ovarian follicular and corpus luteum function. This workshop was sponsored by the Center of Population Research, Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland. We also acknowledge the support of The Channing-Weinberg Company, Mr. Henry Burckhardt, The Merck Institute for Experimental Research, The Ortho Pharmaceutical Company, The Expanded Program for Human Reproduction of the World Health Organization, and The University of Miami. We thank the organizing committee consisting of Drs. Hans Lindner, Georgianna Jagiello, Neena Schwartz, Rees Midgley, Gil Greenwald, Andrew Nalbandov, Sheldon Segal, Julia Labotsky, and Griff Ross for their generous assistance in setting up the program. We also thank the chairpersons of each session for their skillful work and for using their expertise in keeping the discussions to the point. We also are grateful to them for editing the written discussions. Chairpersons included Drs. Robert J. Ryan, Roy O. Greep, Allen W. Schuetz, Neena B. Schwartz, John M. Marsh, John W. Wilks, Hans R. Lindner, and Scheldon J. Segal. Special thanks go to all the invited speakers, discussants, participants and particularly Dr. Irving Rothchild for his summing up remarks. The above organization of Ms. Betty Howard and her staff is gratefully acknowledged. The above secretarial assistance of Ms. Gail Williams, Ms. Evelyn Wisowaty, Ms. Theda Smith and Ms.