This booklet is concerned with the area of clinical depression. Questions about clinical depression are briefly answered in an overview section and are examined in greater detail in the five chapters that follow. In chapter 1, depression is defined and various types of depression are identified. The origins of depression are explored in the second chapter and factors such as sex, age, and other demographic variables are discussed. The role of genetic transmission in clinical depression is examined, and the functions of the brain and neuroendocrine system in clinical depression are explained. Other factors contributing to depression are described: psychophysiology, health and physical illness, personality, cognition, behavior, and life events. The third chapter looks at depression in children and in the elderly and the fourth chapter examines the relationship between depression and suicide. Treatment alternatives are discussed in the fifth chapter, including psychotherapies (cognitive/behavioral therapy, behavior therapy, psychodynamic psychotherapy); pharmacotherapy (tricyclic antidepressants, monoamine oxidase inhibitors, lithium); and electroconvulsive treatment. Current National Institute of Mental Health research programs are listed and briefly described in the conclusion and a table is included which offers suggestions for when and where to seek help. (NRB)