The 3rd edition, the first new one in ten years, includes coverage of molecular levels of detail arising from the last decade's explosion of information at this level of organismic organization. There are 5 new Associate Editors and about 2/3 of the chapters have new authors. Chapters prepared by return authors are extensively revised. Several new chapters have been added on the topic of pregnancy, reflecting the vigorous investigation of this topic during the last decade.

The information covered includes both human and experimental animals; basic principels are sought, and information at the organismic and molecular levels are presented.