'Borderline' is the most slippery of diagnostic categories - by definition something marginal, something in-between, 'something that changes but remains approximately and recognizably the same,' in the words of one contributor to these pages. Augmenting the ambiguity is what editor and eminent child psychiatrist Kenneth S. Robson acknowledges is the 'inherent instability of the diagnostic process in childhood.' A group of outstanding clinicians offers solid support for fellow practitioners by sharing a range of authoritative approaches - descriptive, biological, and psychodynamic - to the population of seriously disturbed children labeled borderline.