The editor of these volumes has asked me to contribute a brief foreword. When I accepted this honor I suddenly became aware of the enormous progress that has taken place in this field in the 50 years since I began as a medical student, in a humble way, to take interest in the catecholamine system. At about that time some evidence was forthcoming to the effect that catecholamines were an important factor in eliciting emotional reactions, thus secondarily influencing behavior. The great physiologist Walter B. Cannon showed in his classic experiments that when a cat was exposed to a dog it responded not only with overt signs of aversion and dislike, but also with an increased flow of adrenaline from its adrenals. The relationships between catecholamines and behavior have since then become the subject of intense research by physiologists, pharmacologists, and psychologists. Infu- sion of adrenaline in man was shown to provoke a typical pattern of emo- tional and behavioral changes. The development of more convenient methods for the measurement of catecholamines in blood and urine led to important new findings. A close association between emotional stress and catecholamine release could be es- tablished. This was further extended to psychiatric disorders in which characteristic disturbances in catecholamine release patterns were described.