Psychoanalytic theories describe defense mechanisms and object relations as psychological structures that have functions vital to personality regulation. In theory, these structures develop in stages and emerge as a coordinated, stable system in early adulthood. However, different levels of maturity of systemic function predominate in various individuals so that people exhibit levels of personality organization (LPO; Kernberg, 1975) differing in degree of maturity. Moreover, the various LPO of adults parallel various developmental stages of maturity of these structures in childhood and predispose to varying psychopathologies. We call this the parallelism hypothesis: Adult LPO parallels the stages of childhood development of these structures. In 2 studies (Study 1, students, n = 301; Study 2, diagnosed and presumed normal people, n = 155), we compared indicators of LPO with relative maturity of defenses and object relations using Thematic Apperception Test (Murray, 1943) scales (Cramer, 1991; Westen, Lohr, Silk, Kerber, & Goodrich, 1989). We compared scores to other indicators of participants' LPO. The parallelism hypothesis was largely supported in both studies.