The psychiatric nurse has broadened his role and better defined his functions, using himself as a therapeutic instrument in developing "a therapeutic interpersonal relationship with a person in need of help. The purpose of this study is: 1) to present the interactions between a nurse and a hyperactive patient of a psychiatric ward of a hospital with custodial and therapeutic character; 2) to analyze the nurse's interventions in light of the interpersonal relationship theory. Four encounters were analyzed, from which the authors were able to observe: the level of involvement and commitment present in each encounter; the increasing ability of the nurse to observe and intervene; moments of patient and nurse's anxiety and situations of inadequate and therapeutic interventions