Since 1948, the date of publication of Hormones and Behavior by Dr. Frank Beach, this hybrid area has received a great deal of attention from scientists representing various allied fields. As a result, the data and publications dealing with hormones and be­ havior have increased geometrically and on an annual basis. More recently, a number of review articles and short volumes dealing with aspects of hormones and behavior have been published. How­ ever, there seemed to be an overwhelming need for a synopsis of the major topics in a unified and integrated form. Thus, the reason for this edition. In these two volumes, we hope we have presented a critical assessment of the various interrelated areas dealing with hormones and behavior. In some instances, we have minimized the presenta­ tion of certain aspects of psychoendocrinology. This was a con­ scious effort since some areas have received competent coverage in other volumes. In other instances, we have presented hitherto seldom mentioned material. For example, we are presenting coverage of the general areas dealing with hormones and behavior in aging and the aging process, mental illness, early experience, motivation, genetics and personality. In some instances, the available data is overabundant; in others, the data is scarce. However, we hope that an evaluation of this situation stimulates further interest and further collaborative research where needed.