Zanarini and Frankenburg described the ‘essential nature’ of borderline psychopathology as involving intense and chronic inner pain deriving from a hyperbolic temperament that is mediated through interpersonal behaviours. These interpersonal behaviours can either provoke kindling events that promote the expression of borderline pathology or buffer against borderline symptoms. This study was designed to test this general hypothesis and to articulate both the temperamental and the mediating constructs implicated in this theory more specifically. A questionnaire containing the elements of this theory was administered to non-clinical (n = 545), clinical (n = 316) and treatment (n = 50) samples. Covariance analyses supported a hyperbolic temperament factor and four mediating factors labelled as passive, agentic, validation seeking and detached. Overall, validity correlations conformed to predictions in showing a strong association between hyperbolic temperament and borderline and other forms of personality pathology and in demonstrating varying relations between the mediating factors and adaptivity, including psychiatric improvements in a treatment trial. The place of this theoretical model of borderline pathology beside other theories that tend to emphasize personality traits or interpersonal patterns are discussed, and clinical implications of the model are highlighted. Copyright © 2011 John Wiley & Sons, Ltd.