In deference to Freud's ingenious predictions of the future potential of the biological sciences concerning psychoanalytic tenets and clinical disorders, an attempt is made to bring the concepts of the Three Polarities, life and death instincts, the Unconscious, and repression into association with relevant anatomical, neurophysiological, and neurochemical data. Implications for diagnosis and therapy were considered in the light of recent and anticipated neurobiological advances. Building bridges between biologic and physiologic processes is exceedingly complicated by the enormous complexities of both fields. There is good reason to hope that the speculative nature which at this time pervades our bridging efforts will eventually be substituted by unequivocal facts and deductions.