This paper elucidates the contributions of child analysis to the treatment of adult patients by examining the interplay of play, containment, and countertransference in the analyst’s work with a disruptive, enuretic/encopretic child. Drawing on clinical vignettes from the analysis of a five-year-old boy, the authors illuminate how child analysis affords unparalleled access to primitive layers of the unconscious. Intense countertransference reactions evoked by children offer crucial opportunities for deepening the analyst’s capacity to tolerate primitive anxieties and rage without retaliating or reacting defensively. Learning to recognize and contain these powerful affective experiences with children can enhance the analyst’s capacity to interpret and work through infantile transferences and regressive transference in adult analyses. The authors suggest that insights gleaned from child analysis enrich the analysts’ ability to effectively treat adults.