 Blockage of the transverse abdomen TAP promotes excellent analgesia of the abdominal wall and the parietal peritoneum. The TAP block could advange the postoperative pain of Appendectomy in children. The world literature doesn t focus the best Ropivacaine s concentration to improve postoperative pain in Appendectomy in children. We propose a randomized trial that compares 3 groups children submitted Appendectomy in children between 6 and 16 years. The control group has received no blockade, the other two groups have received TAP blocks if ropivacaine 0,25 and 0,5 0.4mlkg. 