This paper elaborates key areas of Anna Freud's theory of development, setting these in the context of Freud's structural model and its influence on her early work. The centrality of the role of the ego and the beginnings of one of her major achievements, the elaboration of a psychoanalytic developmental psychology, are shown in evidence in 1936, in The Ego and the Mechanisms of Defence. The author develops this theme in an exploration of the 1965 work Normality and Pathology in Childhood, looking from the base of normal development, via defence and conflict, to regression and significant developmental factors.