This is the first report of the Personality Assessment Interview (PAI), a new clinical and research instrument designed to address the need for a theoretically sound, clinically relevant, comprehensive yet easily administered method for assessing personality organization. By personality organization we mean those structures that stabilize the mental apparatus and become the underlying matrix from which behavioral traits and symptoms develop. Following Otto Kernberg, we define three basic structural constellations: neurotic, borderline and psychotic (Kernberg 1976). The paper describes the interview technique, the hypotheses on which it rests and its aims and structure.