It is the purpose of this volume to present a representative sampling of those neural and hormonal studies which have been the focus of the most intense interest in the recent gerontological research. To this end we have been fortunate to enlist the aid of some of the most competent and innovative investigators in the field. More than this, however, an attempt has been made to provide detailed methodological as well as theoretical evaluation for the areas considered. It is our hope that those researchers interested in this area of regulation during aging will be able to utilize the information contained herein as a basis both for critical analysis as well as for the designing and execution of further experiments in this more important area.