The benefits of the regional anaesthesia are well documented, nevertheless, it does not manage to be imposed to the general anaesthesia by the high index of failures and the potential risk of serious complications, partly due to the fact of realizing the techniques blindly. Nevertheless, the recent discoveries support the use of the ultrasounds as guide for the accomplishment of regional anaesthesia, including the paediatric population. This article tries to introduce us in the regional paediatric anaesthesia guided for ultrasonography and its application in ambulatory surgery (AU)