Endocrine Replacement Therapy in Clinical Practice, an update of Hormone Repla- ment Therapy published by Humana Press in 1999, aims to assist the endocrinologist, gynecologist, pediatrician, urologist, general surgeon, neurologist, neurosurgeon, p- chiatrist, generalist, and trainee in management of their patients with hormonal defici- cies or altered hormonal synthesis or responses. Many new authors have added several new chapters, and all of the previous chapters have been updated. Endocrine testing used to diagnose endocrine disorders and monitor hormone replacement therapy is reviewed. However, detailed discussion of physiology and pathophysiology is not an aim of this book, and these topics are covered in other volumes on endocrinology. Although no one is considered an expert in all areas of endocrine replacement therapy, each of the authors here have extensive knowledge and experience in the management of patients with s- cific endocrine disorders requiring hormone replacement treatment. Although some differences of opinion exist among experts in replacement therapy, each writer has attempted to give a balanced, unbiased recommendation. When com- rable regimens exist, the authors have made this apparent to the reader who can then choose the best treatment for the individual patient. Cost, therapeutic effectiveness, and route of administration are all important considerations in making the final selection of replacement therapy.