This fourth volume, entitled *Writings on Metapsychology and the Clinic of Regression and Sustaining and Interpreting (1952-1955)*, continues the publication in Spanish of the *Complete Works* of Donald W. Winnicott. The *Complete Works* have been compiled, edited, and annotated by a team of Winnicottian scholars. Presented chronologically in 12 volumes, the English psychoanalyst's *Complete Works* comprise a collection of clinical observations, consultations with children, psychoanalytic texts, correspondence, and previously unpublished works on topics that remain relevant to contemporary readers (such as childhood mental health, motherhood, and his concepts of "good enough mother" and "transitional object"). This fourth volume features an introduction by Dominique Scarfone, along with an introduction by Lilian Tuane, who is a member of the Spanish translation committee. The reader will also benefit from exhaustive annotation and commentary by the editors, which provide context to each of Winnicott's works, in conjunction with the annotation work done by the translation committee, which marks the choice of certain concepts over others in our language.