Within the last two decades endocrinological research has taken a definite tum toward biochemistry and molecular biology. This has resulted in a new discipline called' 'molecular endocrinology. " Studies on the mechanism of hormone action have continued to make headlines with fundamental discov eries in receptor action and gene regulation. Recently the insect endocrino logists have also begun to explore the molecular mechanism of steroid hor mone action taking advantage of the vast number of Drosophila mutants, the library of Drosophila gene, and several well-characterized cell-lines. The availability ofthe recombinant DNA technology has provided a truly revolu tionary tool in the hands of the molecular endocrinologists. "Gene Regula tion by Steroid Hormones" is compiled and presented in this frontier spirit, and we hope that this volume will serve not only the active investigators in the field but will also be very useful to students and researchers with a gen eral interest in regulatory biology. The book is an offshoot of the Conference on Molecular Mechanism of Steroid Hormone Action held at the Meadow Brook Mansion of Oakland University in the fall of 1978. We wish to acknowledge the financial assist ance from the National Science Foundation and Oakland University. The conferees will never forget the warmest hospitality of Dr. LOWELL EKLUND and his staff at the Meadow Brook center and we also wish to express per sonal gratitude to many of our students and colleagues for helping us to make the conference a great success.