Having accepted the task to organize, in Amsterdam, an international Congress in behalf of the International Sodety for Neurovegetati'V'e Research such as is held every second year, it occurred to me that it might be worth­ while to change its usual pattern somewhat. Instead of giving merely the opportunity for l'eading a nurnber of rather short free papers, more or less grouped in many categories, we decided to start with a symposium on a special topic 'to be dealt with from several aspects by a numbe·r of invited speakers, the last day of the congress being only available for short free communications. The central topic for the symposium finally chosen was "Neurohormones and N eurohumors" as this subject is of interest :to many morphologists, physiologists, pharmacologists, neuro-endocrinologists, biochemists and clini­ cians, and belongs to a rapidly expanding Held of research. Moreover, it appeared to us that there is some confusion about the defini­ tion of these terms which are not seLdom used indifferently. I hoped that such a symposium would contribute 1to a clearer apprehension of the terms based on morphological, physiological and biochemical criteria as well as to a clearer understanding of some problems involved which will have to be subjects of future investigations.