This paper presents a detailed theoretical discussion of destructive narcissism in relation to Freud and Rosenfeld and later theorists. In destructive narcissism, the destructiveness is itself idealised and overrides "the vital functions which serve the purpose of self-preservation" (Freud, S., 1914, "On narcissism" S.E. 14: 87)--a feature which is essential to Freud's theory of narcissism and Rosenfeld's theories. Adolescents may move into or away from destructive narcissism, either in a relatively transient way, or more chronically leading to an internalised pathological organisation that is part of character structure. We emphasise the need to understand and interpret in their clinical context movements towards and away from destructive narcissism. Two examples are given from an adolescent unit, one an assessment of an anorexic girl (DF), and in the second half of the paper a detailed clinical account (HS) of internal movements in a highly disturbed adolescent who is nonetheless able to turn away from destructive narcissism and make significant progress.