In a discussion of the article on genetic determinants of borderline conditions by Siever and Gunderson, a phenotypic continuum between pure schizotypal and pure affective conditions is postulated. Many “borderline” cases are seen as attenuated forms of schizophrenia, schizoaffective psychosis, or manic-depression. A Venn diagram illustrates differences among syndromes described by Gunderson, Kernberg, Spitzer, and Klein (“hysteroid dysphoria”). Evidence is presented suggesting that Gunderson's borderline syndrome contains more schizotypal individuals than Kernberg's, whereas hysteroid dysphoria is nearer the affective pole of the continuum. A second diagram illustrates how the strength and nature of the genetic factors vary according to the syndrome.