A study led by the CIM of the Hospital de Sant Pau and the Research Institute of San Pablo seeks to prove that children who have enjoyed the accompaniment of the clowns of the Hospital, Pallapupas, present less stress at the time of being operated. This is a controlled clinical trial carried out with the aim of assessing the effectiveness of the Pallapupas’ participation in reducing stress in children undergoing General Surgery by determining the concentration of cortisol in saliva. The study focuses on children between the ages of 5 and 12 undergoing this type of surgery on an outpatient basis in the Sant Pau. Anesthesia, Paediatric Surgery and CIM teams have participated in this study.