Introduction: Pediatric postoperative delirium is a frequent complication for which preventive pharmacological measures have been suggested. The use of midazolam as a prophylactic strategy has not yet been thoroughly assessed. Notwithstanding the fact that it is used in pediatric presurgical separation anxiety, its role in delirium is yet to be established. 
 Objective: To quantify the incidence of pediatric postoperative delirium in patients undergoing low risk surgical interventions, exposed to oral midazolam-based premedication and to explore the protective and risk factors associated with the development of delirium. 
 Materials and methods: Prospective, analytical observational study with a cohort design. Children were conveniently selected in accordance with the daily list of surgical procedures in the operating rooms. The inclusion criteria were children between 2 and 10 years old, ASA I-II, undergoing low risk surgeries. Concurrent and longitudinal follow-up was then conducted upon admission to the post-anesthesia care unit (PACU) for the first hour.
 Results: A total of 518 children were included. The overall incidence of delirium was 14.4 % (95 % CI: 11.4 %-17.5 %). In the subgroup exposed to midazolam, 178 children were analyzed, with an incidence of delirium of 16.2% (95% CI of 10,8 %-21,7). These patients exhibited a higher tendency to delirium with the use of sevoflurane or fentanyl, and/or when presenting with severe postoperative pain. Patients exposed to propofol and/or remifentanil showed lower incidences.
 Conclusions: No reduction in the incidence of emergency pediatric delirium associated with the use of pre-surgical oral midazolam in low risk surgical procedures. Prospective controlled trials and additional research are required to study the effectiveness and safety of this intervention.