Individuals' identity formation is generally understood to occur at multiple levels. Extant research distinguishes two levels of personal identity: (a) an external sense of personal identity that is formed by family, school, and community interactions and (b) a core internal sense of personality identity that is generally understood to be formed during infancy and childhood by caregivers. Fundamental to this core sense of self is that it is continuously experienced as being present. Evidence indicates that trauma and dissociation disrupt the continuous experience of core personal identity resulting in a wide range of psychopathologies including Borderline Personality Disorder (BPD) and Dissociative Identity Disorder (DID) among others. It may also be positively correlated with anxiety, depression, and dependency. A literature search failed to find a psychometrically sound, reliable, and valid, measure of core personal identity let alone a test of discontinuous core personal identity. This article reports efforts to develop and initially validate a highly reliable single factor 37-item (long form) and a 12-item (short form) instrument of discontinuous core personal identity. Both forms correlate significantly and substantially with short measures of Borderline Personality Disorder, interpersonal dependency, generalized anxiety, and depression.