Accurate diagnosis is a key issue in determining treatment mode in borderline patients. The key diagnostic tool is extended observation of the doctor-patient relationship. Basically, borderline patients show partial though varying failure in these ego attributes: self-object differentiation, the capacity to tolerate loss and narcissistic injury, and the internalization of an ego identity and self-esteem that permits autonomy of function and stable personal relations. The author stresses the need to differentiate among patients whose dysfunction stems from: a, problems determined by unresolved intrapsychic conflict; b, regressive