The British psychoanalyst D. W. Winnicott and the American psychoanalyst Phyllis Greenacre were both deeply absorbed by the vicissitudes of the infant's and young child's psychic development. Their clinical observations and theoretical ideas display striking convergences and reciprocal influences. Winnicott was deeply influenced by Greenacre's account of matu-rational processes, an important stimulus to his thinking that originated outside of the British Psychoanalytical Society. Greenacre's writings on early ego development and creativity were influenced by Winnicott's concept of transitional phenomena. The fact that these relationships have remained unexplored until now indicates the need for less insular accounts of the development of psychoanalytic thought on the two sides of the Atlantic.