This paper reports a study aimed at exploring the nursing practices associated with the administration of pro re nata (PRN) postoperative analgesia to children, and at gaining a preliminary understanding of the decisions that nurses make about this important intervention.Nurses are responsible for assessing and administering the appropriate medication at the appropriate time to the child in pain. There was scant published research about the administration of postoperative PRN analgesia to children, or about the decision-making processes inherent in this aspect of clinical nursing care.A sequential mixed methods explanatory study with two data collection phases - quantitative followed by qualitative - was conducted.Nurses used multiple strategies to ascertain children's need for postoperative PRN analgesia, including reference to pain assessment tools, focussing on the behavioural cues of children, involving parents and children, and drawing upon personal and professional backgrounds and experience. Evaluation of the effectiveness of PRN postoperative analgesia was poorly communicated.Decision-making associated with the selection and administration of appropriate analgesia to children is complex. Inservice education should be developed and offered to nurses working with children postoperatively to ensure the appropriate use of PRN pain relief.Documentation surrounding this task is poor and needs to be addressed as a matter of urgency to ensure quality patient outcomes.