SAdness and normal grief are distinguished from pathological grief and depression by intensity, duration, precipitating events, and the quality of psychopathological features. Depression is evaluated as a final common pathway of potential psychodynamic, genetic, psychosocial, physiological, and personality characteristics or events. The clinical entity of depression is diagnosed by describing some of each of the affective, behavioral, and cognitive changes concomitant with depression. The clinical entity of depression is further differentiated for purposes of treatment into the categories of bipolar depression (manic-depressive illness), unipolar depression (psychotic depressive reaction or involutional melancholia), neurotic depression, and secondary depression (secondary to somatic disease, drugs, or to other psychiatric disorders). The immediate treatment depends on the type of depression diagnosed. Unipolar and bipolar depressions respond to specific pharmacologic therapy and supportive care. Neurotic and characterologic depressions respond to supportive or insight psychotherapy with possible brief adjunctive anti-anxiety or hypnotic medication. All of the treatment modalities, with the possilbe exception of insight psychotherapy, can be effected very adequately by the primary care physician who is given clear diagnostic and assessment guidelines with specific treatment approaches.