The concept of "spectrum" was first used in clinical medicine to designate a multitude of overlapping conditions of unknown etiology and uncertain treatment. In the area of affective disorders, the concept has been utilized in several different ways. Two main American contributions (Winokur's and Akiskal's) are analyzed. The authors suggest regrouping, under the heading of affective spectrum disorders (ASD), six clinical entities scattered throughout the literature, beyond the typical, well-established diagnostic categories. These entities are strongly rooted in affective disregulation and in a personality type in which "borderline" features seem to provide a common clinical ground. The definition, characteristics and gross clinical indicators of these disorders are presented. Taxonomic zeal should be replaced by a return to broader, more inclusive categories, until better differential criteria are identified. © 1987.