This monograph brings together our work concerning the relationships be tween the hypothalamus, pituitary and testis. The studies span approximate ly a decade of collaborative work. Over this period our contributions and those of many others have advanced greatly our understanding of many aspects of male reproductive biology. This monograph attempts to survey these developments and to highlight many unresolved issues. It also provides an opportunity to demonstrate the value of investigations which relate bio chemical to structural parameters and to illustrate the importance of animal studies...